Valentin, E, Bottomley, AL, Chilambi, GS, Harry, EJ, Amal, R, Sotiriou, GA, Rice, SA & Gunawan, C 2020, 'Heritable nanosilver resistance in priority pathogen: A unique genetic adaptation and comparison with ionic silver and antibiotics', Nanoscale, vol. 12, no. 4, pp. 2384-2392.View/Download from: Publisher's site
© 2020 The Royal Society of Chemistry. The past decade has seen the incorporation of antimicrobial nanosilver (NAg) into medical devices, and, increasingly, in everyday 'antibacterial' products. With the continued rise of antibiotic resistant bacteria, there are concerns that these priority pathogens will also develop resistance to the extensively commercialized nanoparticle antimicrobials. Herein, this work reports the emergence of stable resistance traits to NAg in the WHO-listed priority pathogen Staphylococcus aureus, which has previously been suggested to have no, or very low, capacity for silver resistance. With no native presence of genetically encoded silver defence mechanisms, the work showed that the bacterium is dependent on mutation of physiologically essential genes, including those involved in nucleotide synthesis and oxidative stress defence. While some mutations were uniquely associated with resistance to NAg, the study also found common mutations that could be protective against both NAg and ionic silver. This is consistent with the observation of NAg/ionic silver cross-resistance. These mutations were detected following withdrawal of the silver exposure, denoting heritable characteristics that allow for spread of the resistance traits even with discontinued silver use. Heritable silver resistance in priority pathogen cautions that these nanoparticle antimicrobials should only be used as needed, to preserve their efficacy for treating infections.
Toh, S-L, Lee, BB, Simpson, JM, Rice, SA, Kotsiou, G, Marial, O & Ryan, S 2020, 'Effect of probiotics on multi-resistant organism colonisation in persons with spinal cord injury: secondary outcome of ProSCIUTTU, a randomised placebo-controlled trial', SPINAL CORD.View/Download from: Publisher's site
Almohaywi, B, Yu, TT, Iskander, G, Chan, DSH, Ho, KKK, Rice, S, Black, DS, Griffith, R & Kumar, N 2019, 'Dihydropyrrolones as bacterial quorum sensing inhibitors.', Bioorganic & medicinal chemistry letters, vol. 29, no. 9, pp. 1054-1059.View/Download from: UTS OPUS or Publisher's site
Bacteria regulate their pathogenicity and biofilm formation through quorum sensing (QS), which is an intercellular communication system mediated by the binding of signaling molecules to QS receptors such as LasR. In this study, a range of dihydropyrrolone (DHP) analogues were synthesized via the lactone-lactam conversion of lactone intermediates. The synthesized compounds were tested for their ability to inhibit QS, biofilm formation and bacterial growth of Pseudomonas aeruginosa. The compounds were also docked into a LasR crystal structure to rationalize the observed structure-activity relationships. The most active compound identified in this study was compound 9i, which showed 63.1% QS inhibition of at 31.25 µM and 60% biofilm reduction at 250 µM with only moderate toxicity towards bacterial cell growth.
Keshvardoust, P, Huron, VAA, Clemson, M, Constancias, F, Barraud, N & Rice, SA 2019, 'Biofilm formation inhibition and dispersal of multi-species communities containing ammonia-oxidising bacteria', NPJ BIOFILMS AND MICROBIOMES, vol. 5.View/Download from: UTS OPUS or Publisher's site
Lema, KA, Constancias, F, Rice, SA & Hadfield, MG 2019, 'High bacterial diversity in nearshore and oceanic biofilms and their influence on larval settlement by Hydroides elegans (Polychaeta)', Environmental Microbiology, vol. 21, no. 9, pp. 3472-3488.View/Download from: UTS OPUS or Publisher's site
© 2019 Society for Applied Microbiology and John Wiley & Sons Ltd. Settlement of many benthic marine invertebrates is stimulated by bacterial biofilms, although it is not known if patterns of settlement reflect microbial communities that are specific to discrete habitats. Here, we characterized the taxonomic and functional gene diversity (16S rRNA gene amplicon and metagenomic sequencing analyses), as well as the specific bacterial abundances, in biofilms from diverse nearby and distant locations, both inshore and offshore, and tested them for their ability to induce settlement of the biofouling tubeworm Hydroides elegans, an inhabitant of bays and harbours around the world. We found that compositions of the bacterial biofilms were site specific, with the greatest differences between inshore and offshore sites. Further, biofilms were highly diverse in their taxonomic and functional compositions across inshore sites, while relatively low diversity was found at offshore sites. Hydroides elegans settled on all biofilms tested, with settlement strongly correlated with bacterial abundance. Bacterial density in biofilms was positively correlated with biofilm age. Our results suggest that the localized distribution of H. elegans is not determined by ‘selection’ to locations by specific bacteria, but it is more likely linked to the prevailing local ecology and oceanographic features that affect the development of dense biofilms and the occurrence of larvae.
Panigrahi, R, Oh, HS, Sharma, V, Lee, KWK, Rice, SA, Cohn, D & Ramanujan, RV 2019, 'Remote control of biofouling by heating PDMS/MnZn ferrite nanocomposites with an alternating magnetic field', Journal of Chemical Technology and Biotechnology, vol. 94, no. 8, pp. 2713-2720.View/Download from: UTS OPUS or Publisher's site
© 2019 Society of Chemical Industry BACKGROUND: The accumulation of unwanted microorganisms on wetted surfaces, leading to surface damage and contamination, is a common and significant global issue. RESULTS: Herein, we report a novel technique where the growth of microorganisms can be readily controlled by coating the surfaces with a polydimethylsiloxane (PDMS)/Mn0.8Zn0.2Fe2O4 (manganese-zinc ferrite) nanocomposite followed by applying alternating magnetic field (AMF). The PDMS/MnZn ferrite nanocomposite is light weight and thermally stable (up to ∼ 330 °C) that can form a flexible coating. PDMS also provides hydrophobicity, which is further enhanced by the addition of Mn and Zn. The improved hydrophobicity makes the coated surface less susceptible to biofilm formation. When external AMF was applied to nanocomposites containing various MnZn ferrite nanoparticle loads of 10%, 20% and 30%, the temperature of the surface of nanocomposites reached to 80, 120 and 160 °C, respectively. Successful biofilm deactivation was achieved by heating the nanocomposites via AMF application, as shown in the biofilm test where up to ∼ 70% of the Pseudomonas aeruginosa PAO1 biofilm cells were killed when the AMF was applied for 20 min to the nanocomposites containing 30% nanoparticles. CONCLUSION: Coating the surface with PDMS/MnZn ferrite nanocomposites followed by applying external AMF can be an effective way to remove biofilm remotely in a wide range of applications. © 2019 Society of Chemical Industry.
Sankaran, J, Tan, NJHJ, But, KP, Cohen, Y, Rice, SA & Wohland, T 2019, 'Single microcolony diffusion analysis in Pseudomonas aeruginosa biofilms', npj Biofilms and Microbiomes, vol. 5, no. 1.View/Download from: UTS OPUS or Publisher's site
Subedi, D, Kohli, GS, Vijay, AK, Willcox, M & Rice, SA 2019, 'Accessory genome of the multi-drug resistant ocular isolate of Pseudomonas aeruginosa PA34.', PloS one, vol. 14, no. 4.View/Download from: UTS OPUS or Publisher's site
Bacteria can acquire an accessory genome through the horizontal transfer of genetic elements from non-parental lineages. This leads to rapid genetic evolution allowing traits such as antibiotic resistance and virulence to spread through bacterial communities. The study of complete genomes of bacterial strains helps to understand the genomic traits associated with virulence and antibiotic resistance. We aimed to investigate the complete accessory genome of an ocular isolate of Pseudomonas aeruginosa strain PA34. We obtained the complete genome of PA34 utilising genome sequence reads from Illumina and Oxford Nanopore Technology followed by PCR to close any identified gaps. In-depth genomic analysis was performed using various bioinformatics tools. The susceptibility to heavy metals and cytotoxicity was determined to confirm expression of certain traits. The complete genome of PA34 includes a chromosome of 6.8 Mbp and two plasmids of 95.4 Kbp (pMKPA34-1) and 26.8 Kbp (pMKPA34-2). PA34 had a large accessory genome of 1,213 genes and had 543 unique genes not present in other strains. These exclusive genes encoded features related to metal and antibiotic resistance, phage integrase and transposons. At least 24 genomic islands (GIs) were predicated in the complete chromosome, of which two were integrated into novel sites. Eleven GIs carried virulence factors or replaced pathogenic genes. A bacteriophage carried the aminoglycoside resistance gene (AAC(3)-IId). The two plasmids carried other six antibiotic resistance genes. The large accessory genome of this ocular isolate plays a large role in shaping its virulence and antibiotic resistance.
Subedi, D, Vijay, AK, Rice, SA & Willcox, M 2019, 'Cytotoxic factor influencing acquired antimicrobial resistance in Pseudomonas aeruginosa', Microbiology Australia, vol. 40, no. 4, pp. 161-164.View/Download from: UTS OPUS or Publisher's site
© 2019 CSIRO. All rights reserved. The Gram-negative opportunistic bacterium Pseudomonas aeruginosa is associated with different types of human infections and because of emerging multidrug-resistant strains, these infections are of major global public health concern. Certain strains possess a unique cytotoxic effector protein ExoU, which contributes to the fitness of this organism in different ecological niches and is associated with acquired antibiotic resistance. This article summarises the current knowledge of the exoU gene in P. aeruginosa, including genetics, distribution in strains from different locations and association with antibiotic resistance. Understanding of this effector protein may have important implications for the understanding of pathogenesis and antimicrobial resistance in P. aeruginosa infections.
Summers, S, Freckelton, ML, Nedved, BT, Rice, SA & Hadfield, MG 2019, 'Complete Genome Sequence of Thalassotalea euphylliae Strain H2.', Microbiology resource announcements, vol. 8, no. 4.View/Download from: UTS OPUS or Publisher's site
A bacterial isolate of Thalassotalea euphylliae H2 was collected from the coral Montipora capitata. MinION long reads were employed for scaffolding and complemented with short-read MiSeq sequences to permit complete genome assembly. The genome is approximately 4.36 Mb long, with 3,669 protein-coding genes, 92 tRNAs, and 21 rRNAs.
Zhu, X, Rice, SA & Barraud, N 2019, 'Nitric Oxide and Iron Signaling Cues Have Opposing Effects on Biofilm Development in Pseudomonas aeruginosa.', Applied and environmental microbiology, vol. 85, no. 3.View/Download from: UTS OPUS or Publisher's site
While both iron and nitric oxide (NO) are redox-active environmental signals shown to regulate biofilm development, their interaction and roles in regulating biofilms have not been fully elucidated. In this study, exposure of Pseudomonas aeruginosa biofilms to exogenous NO inhibited the expression of iron acquisition-related genes and the production of the siderophore pyoverdine. Furthermore, supplementation of the culture medium with high levels of iron (100 μM) counteracted NO-induced biofilm dispersal by promoting the rapid attachment of planktonic cells. In the presence of iron, biofilms were found to disperse transiently to NO, while the freshly dispersed cells reattached rapidly within 15 min. This effect was not due to the scavenging of NO by free iron but involved a cellular response induced by iron that led to the elevated production of the exopolysaccharide Psl. Interestingly, most Psl remained on the substratum after treatment with NO, suggesting that dispersal involved changes in the interactions between Psl and P. aeruginosa cells. Taken together, our results suggest that iron and NO regulate biofilm development via different pathways, both of which include the regulation of Psl-mediated attachment. Moreover, the addition of an iron chelator worked synergistically with NO in the dispersal of biofilms.IMPORTANCE Nitric oxide (NO), which induces biofilm dispersal, is a promising strategy for biofilm control in both clinical and industrial contexts. However, competing environmental signals may reduce the efficacy of NO. The results presented here suggest that the presence of iron represents one such environmental cue that antagonizes the activity of NO as a biofilm-dispersing agent. Based on this understanding, we developed a strategy to enhance dispersal by combining NO with an iron-scavenging agent. Overall, this study links two important environmental signals, iron and NO, with their roles in biofilm development and suggests new ways for improving th...
Jo, Y, Johir, MAH, Cho, Y, Naidu, G, Rice, SA, McDougald, D, Kandasamy, J, Vigneswaran, S & Sun, S 2019, 'A comparative study on nitric oxide and hypochlorite as a membrane cleaning agent to minimise biofilm growth in a membrane bioreactor (MBR) process', Biochemical Engineering Journal, vol. 148, pp. 9-15.View/Download from: UTS OPUS or Publisher's site
© 2019 Elsevier B.V. Reverse osmosis concentrates (ROC) produced from water reclamation plants can threaten the environment if it is not appropriately treated before discharge. A membrane bioreactor (MBR) process to treat ROC was used in this project. In an MBR, fouling is an essential and inevitable phenomenon which leads to higher operational and capital costs. A comparative study on chemical cleaning, such as sodium hypochlorite (NaOCl) and nitric oxide (NO), was experimentally evaluated together with the influence of filtration flux. Exposure to a low concentration of NO reduced biofilms in an MBR system. NO treatment delayed the formation of new biofilm biomass on the membrane. NO also showed good performance in reducing membrane fouling and had no adverse effect on activated sludge and the environment. In MBR, the bacterial community was dominated by Proteobacteria (61%), with Alpha and Beta-proteobacteria representing approximately 54% of the community. After NO treatment, the relative abundance of the Proteobacteria decreased to 44%, and this was also reflected in a reduction in Alpha and Beta-proteobacteria, to 30% and 5% respectively. Thus, NO treatment resulted in the decrease of the relative biofilms associated with reduced MBR performance.
Toh, S-L, Lee, BB, Ryan, S, Simpson, JM, Clezy, K, Bossa, L, Rice, SA, Marial, O, Weber, GH, Kaur, J, Boswell-Ruys, CL, Goodall, S, Middleton, JW, Tuderhope, M & Kotsiou, G 2019, 'Probiotics [LGG-BB12 or RC14-GR1] versus placebo as prophylaxis for urinary tract infection in persons with spinal cord injury [ProSCIUTTU]: a randomised controlled trial.', Spinal cord, vol. 57, no. 7, pp. 550-561.View/Download from: UTS OPUS or Publisher's site
STUDY DESIGN:Randomised double-blind factorial-design placebo-controlled trial. OBJECTIVE:Urinary tract infections (UTIs) are common in people with spinal cord injury (SCI). UTIs are increasingly difficult to treat due to emergence of multi-resistant organisms. Probiotics are efficacious in preventing UTIs in post-menopausal women. We aimed to determine whether probiotic therapy with Lactobacillus reuteri RC-14+Lactobacillus GR-1 (RC14-GR1) and/or Lactobacillus rhamnosus GG+Bifidobacterium BB-12 (LGG-BB12) are effective in preventing UTI in people with SCI. SETTING:Spinal units in New South Wales, Australia with their rural affiliations. METHODS:We recruited 207 eligible participants with SCI and stable neurogenic bladder management. They were randomised to one of four arms: RC14-GR1+LGG-BB12, RC14-GR1+placebo, LGG-BB12+ placebo or double placebos for 6 months. Randomisation was stratified by bladder management type and inpatient or outpatient status. The primary outcome was time to occurrence of symptomatic UTI. RESULTS:Analysis was based on intention to treat. Participants randomised to RC14-GR1 had a similar risk of UTI as those not on RC14-GR1 (HR 0.67; 95% CI: 0.39-1.18; P = 0.17) after allowing for pre-specified covariates. Participants randomised to LGG-BB12 also had a similar risk of UTI as those not on LGG-BB12 (HR 1.29; 95% CI: 0.74-2.25; P = 0.37). Multivariable post hoc survival analysis for RC14-GR1 only vs. the other three groups showed a potential protective effect (HR 0.46; 95% CI: 0.21-0.99; P = 0.03), but this result would need to be confirmed before clinical application. CONCLUSION:In this RCT, there was no effect of RC14-GR1 or LGG-BB12 in preventing UTI in people with SCI.
Faiz, MB, Amal, R, Marquis, CP, Harry, EJ, Sotiriou, GA, Rice, SA & Gunawan, C 2018, 'Nanosilver and the microbiological activity of the particulate solids versus the leached soluble silver.', Nanotoxicology, vol. 12, no. 3, pp. 263-273.View/Download from: UTS OPUS or Publisher's site
Nanosilver (Ag NPs) is currently one of the most commercialized antimicrobial nanoparticles with as yet, still unresolved cytotoxicity origins. To date, research efforts have mostly described the antimicrobial contribution from the leaching of soluble silver, while the undissolved solid Ag particulates are often considered as being microbiologically inert, serving only as source of the cytotoxic Ag ions. Here, we show the rapid stimulation of lethal cellular oxidative stress in bacteria by the presence of the undissolved Ag particulates. The cytotoxicity characteristics are distinct from those arising from the leached soluble Ag, the latter being locked in organic complexes. The work also highlights the unique oxidative stress-independent bacterial toxicity of silver salt. Taken together, the findings advocate that future enquiries on the antimicrobial potency and also importantly, the environmental and clinical impact of Ag NPs use, should pay attention to the potential bacterial toxicological responses to the undissolved Ag particulates, rather than just to the leaching of soluble silver. The findings also put into question the common use of silver salt as model material for evaluating bacterial toxicity of Ag NPs.
Oh, HS, Constancias, F, Ramasamy, C, Tang, PYP, Yee, MO, Fane, AG, McDougald, D & Rice, SA 2018, 'Biofouling control in reverse osmosis by nitric oxide treatment and its impact on the bacterial community', Journal of Membrane Science, vol. 550, pp. 313-321.View/Download from: UTS OPUS or Publisher's site
© 2018 The Authors Recent discoveries regarding the regulation of the biofilm life cycle by bacterial signaling systems have identified novel strategies for manipulation of biofilm development to control the biofouling of membrane-based water purification systems. Nitric oxide (NO) signaling has been shown to induce dispersal of a wide range of single- and multi-species biofilms. However, the impact of NO-mediated biofilm dispersal on the taxa composition of natural communities as well as the potential selection for non-responding community members have rarely been addressed. Here, we investigated the effect of diethylenetriamine (DETA) NONOate, an NO donor with a long half-life, on biofilm dispersal of a bacterial community responsible for membrane biofouling to address this question. The biofilm of a complex community from a fouled industrial reverse osmosis (RO) membrane was dispersed over 50% by 500 μM of DETA NONOate treatment in a continuous flow system. Once-daily treatment with DETA NONOate in a laboratory-scale RO system demonstrated its anti-biofouling effect by delaying the transmembrane pressure increase during constant-flux filtration. Characterization of the bacterial communities of dispersed cells and remaining biofilm cells using a 16S Illumina MiSeq metabarcoding approach demonstrated that biofilm dispersal by DETA NONOate had no selection bias in the community.
Almohaywi, B, Taunk, A, Wenholz, DS, Nizalapur, S, Biswas, NN, Ho, KKK, Rice, SA, Iskander, G, Black, DS, Griffith, R & Kumar, N 2018, 'Design and Synthesis of Lactams Derived from Mucochloric and Mucobromic Acids as Pseudomonas aeruginosa Quorum Sensing Inhibitors.', Molecules (Basel, Switzerland), vol. 23, no. 5.View/Download from: UTS OPUS or Publisher's site
Bacterial infections, particularly hospital-acquired infections caused by Pseudomonas aeruginosa, have become a global threat with a high mortality rate. Gram-negative bacteria including P. aeruginosa employ N-acyl homoserine lactones (AHLs) as chemical signals to regulate the expression of pathogenic phenotypes through a mechanism called quorum sensing (QS). Recently, strategies targeting bacterial behaviour or QS have received great attention due to their ability to disarm rather than kill pathogenic bacteria, which lowers the evolutionary burden on bacteria and the risk of resistance development. In the present study, we report the design and synthesis of N-alkyl- and N-aryl 3,4 dichloro- and 3,4-dibromopyrrole-2-one derivatives through the reductive amination of mucochloric and mucobromic acid with aliphatic and aromatic amines. The quorum sensing inhibition (QSI) activity of the synthesized compounds was determined against a P. aeruginosa MH602 reporter strain. The phenolic compounds exhibited the best activity with 80% and 75% QSI at 250 µM and were comparable in activity to the positive control compound Fu-30. Computational docking studies performed using the LasR receptor protein of P. aeruginosa suggested the importance of hydrogen bonding and hydrophobic interactions for QSI.
Baek, JS, Tan, CH, Ng, NKJ, Yeo, YP, Rice, SA & Loo, SCJ 2018, 'A programmable lipid-polymer hybrid nanoparticle system for localized, sustained antibiotic delivery to Gram-positive and Gram-negative bacterial biofilms', Nanoscale Horizons, vol. 3, no. 3, pp. 305-311.View/Download from: UTS OPUS or Publisher's site
© 2018 The Royal Society of Chemistry. Bacteria enmeshed in an extracellular matrix, biofilms, exhibit enhanced antibiotic tolerance. Coupled with the rapid emergence of multidrug-resistant strains, the current cohorts of antibiotics are becoming ineffective. Alternative antimicrobial approaches are therefore urgently needed to overcome recalcitrant biofilm infections. Here, we propose the use of a non-toxic lipid-polymer hybrid nanoparticle (LPN) system composed of a solid polymer core (i.e. PLGA; poly lactic-co-glycolic acid) and a cationic lipid shell (i.e. DOTAP) for localized, sustained release of antimicrobial agents to bacterial biofilms. LPNs were synthesized through a simple, robust self-assembly approach. LPNs of uniform particle size (i.e. 100-130 nm), efficiently encapsulated (up to 95%) bioimaging molecules or antibiotics and provided controlled release of the latter. The cationic lipid coating enabled the LPN to anchor onto surfaces of a diverse range of Gram-positive and Gram-negative bacterial pathogens, either in the planktonic or biofilm form. Consistently, the LPN formulations reduced more than 95% of biofilm activity at concentrations that were 8 to 32-fold lower than free antibiotics. These data clearly indicate that these novel formulations could be a useful strategy to enhance the efficacy of antimicrobials against planktonic cells and biofilms of diverse species.
Chew, SC, Yam, JKH, Matysik, A, Seng, ZJ, Klebensberger, J, Givskov, M, Doyle, P, Rice, SA, Yang, L & Kjelleberg, S 2018, 'Matrix Polysaccharides and SiaD Diguanylate Cyclase Alter Community Structure and Competitiveness of Pseudomonas aeruginosa during Dual-Species Biofilm Development with Staphylococcus aureus.', mBio, vol. 9, no. 6.View/Download from: UTS OPUS or Publisher's site
Mixed-species biofilms display a number of emergent properties, including enhanced antimicrobial tolerance and communal metabolism. These properties may depend on interspecies relationships and the structure of the biofilm. However, the contribution of specific matrix components to emergent properties of mixed-species biofilms remains poorly understood. Using a dual-species biofilm community formed by the opportunistic pathogens Pseudomonas aeruginosa and Staphylococcus aureus, we found that whilst neither Pel nor Psl polysaccharides, produced by P. aeruginosa, affect relative species abundance in mature P. aeruginosa and S. aureus biofilms, Psl production is associated with increased P. aeruginosa abundance and reduced S. aureus aggregation in the early stages of biofilm formation. Our data suggest that the competitive effect of Psl is not associated with its structural role in cross-linking the matrix and adhering to P. aeruginosa cells but is instead mediated through the activation of the diguanylate cyclase SiaD. This regulatory control was also found to be independent of the siderophore pyoverdine and Pseudomonas quinolone signal, which have previously been proposed to reduce S. aureus viability by inducing lactic acid fermentation-based growth. In contrast to the effect mediated by Psl, Pel reduced the effective crosslinking of the biofilm matrix and facilitated superdiffusivity in microcolony regions. These changes in matrix cross-linking enhance biofilm surface spreading and expansion of microcolonies in the later stages of biofilm development, improving overall dual-species biofilm growth and increasing biovolume severalfold. Thus, the biofilm matrix and regulators associated with matrix production play essential roles in mixed-species biofilm interactions.IMPORTANCE Bacteria in natural and engineered environments form biofilms that include many different species. Microorganisms rely on a number of different strategies to manage social interactions with ...
Chilambi, GS, Gao, IH, Yoon, BK, Park, S, Kawakami, LM, Ravikumar, V, Chan-Park, MB, Cho, NJ, Bazan, GC, Kline, KA, Rice, SA & Hinks, J 2018, 'Membrane adaptation limitations in: Enterococcus faecalis underlie sensitivity and the inability to develop significant resistance to conjugated oligoelectrolytes', RSC Advances, vol. 8, no. 19, pp. 10284-10293.View/Download from: UTS OPUS or Publisher's site
© 2018 The Royal Society of Chemistry. The growing problem of antibiotic resistant bacteria, along with a dearth of new antibiotics, has redirected attention to the search for alternative antimicrobial agents. Conjugated oligoelectrolytes (COEs) are an emerging class of antimicrobial agents which insert into bacterial cell membranes and are inhibitory against a range of Gram-positive and Gram-negative bacteria. In this study, the extent of COE resistance that Enterococcus faecalis could achieve was studied. Enterococci are able to grow in hostile environments and develop resistance to membrane targeting antibiotics such as daptomycin in clinical settings. Herein we expand our knowledge of the antimicrobial mechanism of action of COEs by developing COE-resistant strains of E. faecalis OG1RF. Evolution studies yielded strains with a moderate 4-16 fold increase in antimicrobial resistance relative to the wild type. The resistant isolates accumulated agent-specific mutations associated with the liaFSR operon, which is a cell envelope-associated stress-response sensing and regulating system. The COE resistant isolates displayed significantly altered membrane fatty acid composition. Subsequent, exogenous supplementation with single fatty acids, which were chosen based on those dominating the fatty acid profiles of the mutants, increased resistance of the wild-type E. faecalis to COEs. In combination, genetic, fatty acid, and uptake studies support the hypothesis that COEs function through insertion into and disruption of membranes and that the mechanism by which this occurs is specific to the disrupting agent. These results were validated by a series of biophysical experiments showing the tendency of COEs to accumulate in and perturb adapted membrane extracts. Collectively, the data support that COEs are promising antimicrobial agents for targeting E. faecalis, and that there is a high barrier to the emergence of severely resistant strains constrained by biological lim...
Doyle, LE, Williams, RBH, Rice, SA, Marsili, E & Lauro, FM 2018, 'Draft Genome Sequence of Enterobacter sp. Strain EA-1, an Electrochemically Active Microorganism Isolated from Tropical Sediment.', Genome announcements, vol. 6, no. 9.View/Download from: UTS OPUS or Publisher's site
Enterobacter sp. strain EA-1 is an electrochemically active bacterium isolated from tropical sediment in Singapore. Here, the annotated draft genome assembly of the bacterium is reported. Whole-genome comparison indicates that Enterobacter sp. EA-1, along with a previously sequenced Enterobacter isolate from East Asia, forms a distinct clade within the Enterobacter genus.
Liu, C, Liew, CW, Wong, YH, Tan, ST, Poh, WH, Manimekalai, SMS, Rajan, S, Xin, L, Liang, Z-X, Grüber, G, Rice, SA & Lescar, J 2018, 'Insights into biofilm dispersal regulation from the crystal structure of the PAS-GGDEF-EAL region of RbdA from Pseudomonas aeruginosa.', Journal of Bacteriology, vol. 200, no. 3.View/Download from: UTS OPUS or Publisher's site
RbdA is a positive Regulator of biofilm dispersal of Pseudomonas aeruginosa Its cytoplasmic region (cRbdA) comprises a N-terminal PAS domain followed by a diguanylate cyclase (GGDEF) and an EAL domain, whose phosphodiesterase activity is allosterically stimulated by GTP binding to the GGDEF domain. We report crystal structures of cRbdA and of two binary complexes: with GTP/Mg2+ bound to the GGDEF active site and with the EAL domain bound to the c-di-GMP substrate. These structures unveil a 2-fold symmetric dimer, stabilized by a closely packed N-terminal PAS domain and a non-canonical EAL dimer. The auto-inhibitory switch is formed by an alpha helix (S-helix) immediately N-terminal to the GGDEF domain that interacts with the EAL dimerization helix (α6-E) of the other EAL monomer and maintains the protein in a locked conformation. We propose that local conformational changes in cRbdA upon GTP binding lead to a structure with the PAS domain and S-helix shifted away from the GGDEF-EAL domains, as suggested by SAXS experiments. Domain reorientation should be facilitated by the presence of a α-helical lever (H-helix) that tethers the GGDEF and EAL regions, allowing the EAL domain to rearrange into an active dimeric conformation.IMPORTANCEBiofilm formation by bacterial pathogens increases resistance to antibiotics. RbdA positively regulates biofilm dispersal of Pseudomonas aeruginosa The crystal structures of the cytoplasmic region of RbdA protein presented here reveal that two evolutionary-conserved helices play an important role in regulating the activity of RbdA, with implications for other dual GGDEF-EAL domains that are abundant in the proteomes of several bacterial pathogens. Thus, this work could assist the development of small molecules that would promote bacterial biofilm dispersal.
Mukherjee, M, Hu, Y, Tan, CH, Rice, SA & Cao, B 2018, 'Engineering a light-responsive, quorum quenching biofilm to mitigate biofouling on water purification membranes.', Science advances, vol. 4, no. 12.View/Download from: UTS OPUS or Publisher's site
Quorum quenching (QQ) has been reported to be a promising approach for membrane biofouling control. Entrapment of QQ bacteria in porous matrices is required to retain them in continuously operated membrane processes and to prevent uncontrollable biofilm formation by the QQ bacteria on membrane surfaces. It would be more desirable if the formation and dispersal of biofilms by QQ bacteria could be controlled so that the QQ bacterial cells are self-immobilized, but the QQ biofilm itself still does not compromise membrane performance. In this study, we engineered a QQ bacterial biofilm whose growth and dispersal can be modulated by light through a dichromatic, optogenetic c-di-GMP gene circuit in which the bacterial cells sense near-infrared (NIR) light and blue light to adjust its biofilm formation by regulating the c-di-GMP level. We also demonstrated the potential application of the engineered light-responsive QQ biofilm in mitigating biofouling of water purification forward osmosis membranes. The c-di-GMP-targeted optogenetic approach for controllable biofilm development we have demonstrated here should prove widely applicable for designing other controllable biofilm-enabled applications such as biofilm-based biocatalysis.
Rice, S, Marsili, E & Kjelleberg, S 2018, 'Mixed community biofilms and microbially influenced corrosion', Microbiology Australia, vol. 39, no. 3, pp. 152-157.View/Download from: UTS OPUS or Publisher's site
Sankaran, J, Karampatzakis, A, Rice, SA & Wohland, T 2018, 'Quantitative imaging and spectroscopic technologies for microbiology', FEMS Microbiology Letters, vol. 365, no. 9.View/Download from: UTS OPUS or Publisher's site
© FEMS 2018. Light microscopy has enabled the observation of the structure and organisation of biofilms. Typically, the contrast in an image obtained from light microscopy is given by the time-averaged intensity that is effective in visualising the overall structure. Technological advancements in light microscopy have led to the creation of techniques that not only provide a static intensity image of the biofilm, but also enable one to quantify various dynamic physicochemical properties of biomolecules in microbial biofilms. Such light microscopy-based techniques can be grouped into two main classes, those that are based on luminescence and those that are based on scattering. Here, we review the fundamentals and applications of luminescence and scattering-based techniques, specifically, fluorescence lifetime imaging, Förster resonance energy transfer, fluorescence correlation spectroscopy, fluorescence recovery after photobleaching, single-particle tracking, transient state imaging, and Brillouin and Raman microscopy. These techniques provide information about the abundance, interactions and mobility of various molecules in the biofilms and also properties of the local microenvironment at optical resolution. Further, one could use any of these techniques to probe the real-time changes in these physical parameters upon the addition of external agents or at different stages during the growth of biofilms.
Sheraton, MV, Yam, JKH, Tan, CH, Oh, HS, Mancini, E, Yang, L, Rice, SA & Sloot, PMA 2018, 'Mesoscopic Energy Minimization Drives Pseudomonas aeruginosa Biofilm Morphologies and Consequent Stratification of Antibiotic Activity Based on Cell Metabolism.', Antimicrobial agents and chemotherapy, vol. 62, no. 5.View/Download from: UTS OPUS or Publisher's site
Segregation of bacteria based on their metabolic activities in biofilms plays an important role in the development of antibiotic resistance. Mushroom-shaped biofilm structures, which are reported for many bacteria, exhibit topographically varying levels of multiple drug resistance from the cap of the mushroom to its stalk. Understanding the dynamics behind the formation of such structures can aid in design of drug delivery systems, antibiotics, or physical systems for removal of biofilms. We explored the development of metabolically heterogeneous Pseudomonas aeruginosa biofilms using numerical models and laboratory knockout experiments on wild-type and chemotaxis-deficient mutants. We show that chemotactic processes dominate the transformation of slender and hemispherical structures into mushroom structures with a signature cap. Cellular Potts model simulation and experimental data provide evidence that accelerated movement of bacteria along the periphery of the biofilm, due to nutrient cues, results in the formation of mushroom structures and bacterial segregation. Multidrug resistance of bacteria is one of the most threatening dangers to public health. Understanding the mechanisms of the development of mushroom-shaped biofilms helps to identify the multidrug-resistant regions. We decoded the dynamics of the structural evolution of bacterial biofilms and the physics behind the formation of biofilm structures as well as the biological triggers that produce them. Combining in vitro gene knockout experiments with in silico models showed that chemotactic motility is one of the main driving forces for the formation of stalks and caps. Our results provide physicists and biologists with a new perspective on biofilm removal and eradication strategies.
Subedi, D, Kohli, GS, Vijay, AK, Willcox, M & Rice, S 2018, 'Accessory genome contributes to the virulence and resistance of the ocular isolate of Pseudomonas aeruginosa: A complete genome analysis'.View/Download from: Publisher's site
Bacteria can acquire an accessory genome through the horizontal transfer of genetic elements from non-parental lineages. This leads to rapid genetic evolution allowing traits such as antibiotic resistance and virulence to spread through bacterial communities. The study of complete genomes of bacterial strains helps to understand the genomic traits associated with virulence and antibiotic resistance. We aimed to investigate the complete accessory genome of an ocular isolate of P. aeruginosa. We obtained the complete genome of the ocular isolate strain PA34 of P. aeruginosa utilising genome sequence reads from Illumina and Oxford Nanopore Technology followed by PCR to close any identified gaps. In-depth genomic analysis was performed using various bioinformatics tools. The phenotypic properties of susceptibility to heavy metals and cytotoxicity were determined to confirm expression of certain traits. The complete genome of PA34 includes a chromosome of 6.8 Mbp and two plasmids of 95.4 Kbp (pMKPA34-1) and 26.8 Kbp (pMKPA34-2). PA34 had a large accessory genome of 1,213 genes and had 543 unique genes not present in other strains. These exclusive genes encoded features related to metal and antibiotic resistance, phage integrase and transposons. At least 24 GIs were predicated in the complete chromosome, of which two were integrated into novel sites. Eleven GIs carried virulence factors or replaced pathogenic genes. A bacteriophage carried the aminoglycoside resistance gene (aac(3)-IId). The two plasmids carried other six antibiotic resistance genes. The large accessory genome of this ocular isolate plays a large role in shaping its virulence and antibiotic resistance.
Subedi, D, Vijay, AK, Kohli, GS, Rice, SA & Willcox, M 2018, 'Association between possession of ExoU and antibiotic resistance in Pseudomonas aeruginosa.', PloS one, vol. 13, no. 9.View/Download from: UTS OPUS or Publisher's site
Virulent strains of Pseudomonas aeruginosa are often associated with an acquired cytotoxic protein, exoenzyme U (ExoU) that rapidly destroys the cell membranes of host cells by its phospholipase activity. Strains possessing the exoU gene are predominant in eye infections and are more resistant to antibiotics. Thus, it is essential to understand treatment options for these strains. Here, we have investigated the resistance profiles and genes associated with resistance for fluoroquinolone and beta-lactams. A total of 22 strains of P. aeruginosa from anterior eye infections, microbial keratitis (MK), and the lungs of cystic fibrosis (CF) patients were used. Based on whole genome sequencing, the prevalence of the exoU gene was 61.5% in MK isolates whereas none of the CF isolates possessed this gene. Overall, higher antibiotic resistance was observed in the isolates possessing exoU. Of the exoU strains, all except one were resistant to fluoroquinolones, 100% were resistant to beta-lactams. 75% had mutations in quinolone resistance determining regions (T81I gyrA and/or S87L parC) which correlated with fluoroquinolone resistance. In addition, exoU strains had mutations at K76Q, A110T, and V126E in ampC, Q155I and V356I in ampR and E114A, G283E, and M288R in mexR genes that are associated with higher beta-lactamase and efflux pump activities. In contrast, such mutations were not observed in the strains lacking exoU. The expression of the ampC gene increased by up to nine-fold in all eight exoU strains and the ampR was upregulated in seven exoU strains compared to PAO1. The expression of mexR gene was 1.4 to 3.6 fold lower in 75% of exoU strains. This study highlights the association between virulence traits and antibiotic resistance in pathogenic P. aeruginosa.
Subedi, D, Vijay, AK, Kohli, GS, Rice, SA & Willcox, M 2018, 'Comparative genomics of clinical strains of Pseudomonas aeruginosa strains isolated from different geographic sites.', Scientific reports, vol. 8, no. 1, pp. 15668-15668.View/Download from: UTS OPUS or Publisher's site
The large and complex genome of Pseudomonas aeruginosa, which consists of significant portions (up to 20%) of transferable genetic elements contributes to the rapid development of antibiotic resistance. The whole genome sequences of 22 strains isolated from eye and cystic fibrosis patients in Australia and India between 1992 and 2007 were used to compare genomic divergence and phylogenetic relationships as well as genes for antibiotic resistance and virulence factors. Analysis of the pangenome indicated a large variation in the size of accessory genome amongst 22 stains and the size of the accessory genome correlated with number of genomic islands, insertion sequences and prophages. The strains were diverse in terms of sequence type and dissimilar to that of global epidemic P. aeruginosa clones. Of the eye isolates, 62% clustered together within a single lineage. Indian eye isolates possessed genes associated with resistance to aminoglycoside, beta-lactams, sulphonamide, quaternary ammonium compounds, tetracycline, trimethoprims and chloramphenicols. These genes were, however, absent in Australian isolates regardless of source. Overall, our results provide valuable information for understanding the genomic diversity of P. aeruginosa isolated from two different infection types and countries.
Subedi, D, Vijay, AK, Kohli, GS, Rice, SA & Willcox, M 2018, 'Nucleotide sequence analysis of NPS-1 β-lactamase and a novel integron (In1427)-carrying transposon in an MDR Pseudomonas aeruginosa keratitis strain', Journal of Antimicrobial Chemotherapy, vol. 73, no. 6, pp. 1724-1726.View/Download from: UTS OPUS or Publisher's site
Summers, S, Freckelton, ML, Nedved, BT, Rice, SA & Hadfield, MG 2018, 'Full-Genome Sequence of Thalassotalea euphylliae H1, Isolated from a Montipora capitata Coral Located in Hawai'i.', Microbiology resource announcements, vol. 7, no. 20, pp. 1-2.View/Download from: UTS OPUS or Publisher's site
The isolate of Thalassotalea euphylliae H1 was collected from the surface of a Montipora capitata coral. The genome was assembled using long reads from a Nanopore MinION sequencer for scaffolding and complemented with short-read MiSeq sequences. The genome was approximately 4.77 Mb long with 4,020 protein-coding genes, 92 tRNAs, and 22 rRNAs.
Topa, SH, Subramoni, S, Palombo, EA, Kingshott, P, Rice, SA & Blackall, LL 2018, 'Cinnamaldehyde disrupts biofilm formation and swarming motility of pseudomonas aeruginosa', Microbiology (United Kingdom), vol. 164, no. 9, pp. 1087-1097.View/Download from: UTS OPUS or Publisher's site
© 2018 The Authors. Bacterial biofilms can cause serious health care complications associated with increased morbidity and mortality. There is an urge to discover and develop new biofilm inhibitors from natural products or by modifying natural compounds or understanding the modes of action of existing compounds. Cinnamaldehyde (CAD), one of the major components of cinnamon oil, has been demonstrated to act as an antimicrobial agent against a number of Gram-negative and Gram-positive pathogens, including Pseudomonas aeruginosa, Helicobacter pylori and Listeria monocytogenes. Despite the mechanism of action of CAD against the model organism P. aeruginosa being undefined, based on its antimicrobial properties, we hypothesized that it may disrupt preformed biofilms of P. aeruginosa. The minimum inhibitory concentration (MIC) of CAD for planktonic P. aeruginosa was determined to be 11.8 mM. Membrane depolarization assays demonstrated disruption of the transmembrane potential of P. aeruginosa. CAD at 5.9mM (0.5 MIC) disrupted preformed biofilms by 75.6% and 3mM CAD (0.25 MIC) reduced the intracellular concentrations of the secondary messenger, bis-(3′–5′)-cyclic dimeric guanosine monophosphate (c-di-GMP), which controls P. aeruginosa biofilm formation. The swarming motility of P. aeruginosa was also reduced by CAD in a concentration-dependent manner. Collectively, these findings show that sub-MICs of CAD can disrupt biofilms and other surface colonization phenotypes through the modulation of intracellular signalling processes.
Zhu, X, Oh, H-S, Ng, YCB, Tang, PYP, Barraud, N & Rice, SA 2018, 'Nitric Oxide-Mediated Induction of Dispersal in Pseudomonas aeruginosa Biofilms Is Inhibited by Flavohemoglobin Production and Is Enhanced by Imidazole.', Antimicrobial agents and chemotherapy, vol. 62, no. 3.View/Download from: UTS OPUS or Publisher's site
The biological signal molecule nitric oxide (NO) was found to induce biofilm dispersal across a range of bacterial species, which led to its consideration for therapeutic strategies to treat biofilms and biofilm-related infections. However, biofilms are often not completely dispersed after exposure to NO. To better understand this phenomenon, we investigated the response of Pseudomonas aeruginosa biofilm cells to successive NO treatments. When biofilms were first pretreated with a low, noneffective dose of NO, a second dose of the signal molecule at a concentration usually capable of inducing dispersal did not have any effect. Amperometric analysis revealed that pretreated P. aeruginosa cells had enhanced NO-scavenging activity, and this effect was associated with the production of the flavohemoglobin Fhp. Further, quantitative real-time reverse transcription-PCR (qRT-PCR) analysis showed that fhp expression increased by over 100-fold in NO-pretreated biofilms compared to untreated biofilms. Biofilms of mutant strains harboring mutations in fhp or fhpR, encoding a NO-responsive regulator of fhp, were not affected in their dispersal response after the initial pretreatment with NO. Overall, these results suggest that FhpR can sense NO to trigger production of the flavohemoglobin Fhp and inhibit subsequent dispersal responses to NO. Finally, the addition of imidazole, which can inhibit the NO dioxygenase activity of flavohemoglobin, attenuated the prevention of dispersal after NO pretreatment and improved the dispersal response in older, starved biofilms. This study clarifies the underlying mechanisms of impaired dispersal induced by repeated NO treatments and offers a new perspective for improving the use of NO in biofilm control strategies.
Gunawan, C, Marquis, CP, Amal, R, Sotiriou, GA, Rice, SA & Harry, EJ 2017, 'Widespread and Indiscriminate Nanosilver Use: Genuine Potential for Microbial Resistance.', ACS Nano, vol. 11, no. 4, pp. 3438-3445.View/Download from: UTS OPUS or Publisher's site
In this era of increasing antibiotic resistance, the use of alternative antimicrobials such as silver has become more widespread. Superior antimicrobial activity has been provided through fabrication of silver nanoparticles or nanosilver (NAg), which imparts cytotoxic actions distinct from those of bulk silver. In the wake of the recent discoveries of bacterial resistance to NAg and its rising incorporation in medical and consumer goods such as wound dressings and dietary supplements, we argue that there is an urgent need to monitor the prevalence and spread of NAg microbial resistance. In this Perspective, we describe how the use of NAg in commercially available products facilitates prolonged microorganism exposure to bioavailable silver, which underpins the development of resistance. Furthermore, we advocate for a judicial approach toward NAg use in order to preserve its efficacy and to avoid environmental disruption.
Bossa, L, Kline, K, McDougald, D, Lee, BB & Rice, SA 2017, 'Urinary catheter-associated microbiota change in accordance with treatment and infection status.', PLoS ONE, vol. 12, no. 6, pp. e0177633-e0177633.View/Download from: UTS OPUS or Publisher's site
The use of long-term catheterisation to manage insensate bladders, often associated with spinal cord injury (SCI), increases the risk of microbial colonisation and infection of the urinary tract. Urinary tract infection (UTI) is typically diagnosed and treated based on the culturing of organisms from the urine, although this approach overlooks low titer, slow growing and non-traditional pathogens. Here, we present an investigation of the urinary tract microbiome in catheterised SCI individuals, using T-RFLP and metagenomic sequencing of the microbial community. We monitored three neurogenic patients over a period of 12 months, who were part of a larger study investigating the efficacy of probiotics in controlling UTIs, to determine how their urinary tract microbial community composition changed over time and in relation to probiotic treatment regimens. Bacterial biofilms adherent to urinary catheters were examined as a proxy for bladder microbes. The microbial community composition of the urinary tract differed significantly between individuals. Probiotic therapy resulted in a significant change in the microbial community associated with the catheters. The community also changed as a consequence of UTI and this shift in community composition preceded the clinical diagnosis of infection. Changes in the microbiota due to probiotic treatment or infection were transient, resolving to microbial communities similar to their pre-treatment communities, suggesting that the native community was highly resilient. Based on these results, we propose that monitoring a patient's microbial community can be used to track the health of chronically catheterized patients and thus, can be used as part of a health-status monitoring program.
Jogdeo, P, Chai, R, Shuyang, S, Saballus, M, Constancias, F, Wijesinghe, SL, Thierry, D, Blackwood, DJ, McDougald, D, Rice, SA & Marsili, E 2017, 'Onset of microbial influenced corrosion (MIC) in stainless steel exposed to mixed species biofilms from equatorial seawater', Journal of The Electrochemical Society, vol. 164, no. 9, pp. C532-C538.View/Download from: UTS OPUS or Publisher's site
© The Author(s) 2017. The understanding of microbial influenced corrosion (MIC) in aerobic mixed biofilms benefits from advanced microscopy and microbial ecology characterization of biofilms. Here, the onset of MIC in stainless steel coupons was studied in both natural and artificial seawater. Rapid selection of biofilm-forming microorganisms from natural seawater was observed for field experiments. Potential ennoblement was observed only in natural seawater. A seawater derived mixed microbial consortium enriched in artificial seawater was used to characterize the effect of several parameters on MIC. The concentration of organic carbon was the major determinant of MIC, while shaking speed and polishing played minor roles. The biofilm was preferentially formed at the grain boundaries. These results outline the need for MIC onset characterization with mixed microbial consortia to predict long-term corrosion behavior of stainless steel in seawater.
Luo, J, Lv, P, Zhang, J, Fane, AG, McDougald, D & Rice, SA 2017, 'Succession of biofilm communities responsible for biofouling of membrane bioreactors (MBRs)', PLOS ONE, vol. 12, no. 7.View/Download from: UTS OPUS or Publisher's site
Atarashi, K, Suda, W, Luo, C, Kawaguchi, T, Motoo, I, Narushima, S, Kiguchi, Y, Yasuma, K, Watanabe, E, Tanoue, T, Thaiss, CA, Sato, M, Toyooka, K, Said, HS, Yamagami, H, Rice, SA, Gevers, D, Johnson, RC, Segre, JA, Chen, K, Kolls, JK, Elinav, E, Morita, H, Xavier, RJ, Hattori, M & Honda, K 2017, 'Ectopic colonization of oral bacteria in the intestine drives TH1 cell induction and inflammation.', Science, vol. 358, no. 6361, pp. 359-365.View/Download from: UTS OPUS or Publisher's site
Intestinal colonization by bacteria of oral origin has been correlated with several negative health outcomes, including inflammatory bowel disease. However, a causal role of oral bacteria ectopically colonizing the intestine remains unclear. Using gnotobiotic techniques, we show that strains of Klebsiella spp. isolated from the salivary microbiota are strong inducers of T helper 1 (TH1) cells when they colonize in the gut. These Klebsiella strains are resistant to multiple antibiotics, tend to colonize when the intestinal microbiota is dysbiotic, and elicit a severe gut inflammation in the context of a genetically susceptible host. Our findings suggest that the oral cavity may serve as a reservoir for potential intestinal pathobionts that can exacerbate intestinal disease.
Feng, S, Tan, CH, Constancias, F, Kohli, GS, Cohen, Y & Rice, SA 2017, 'Predation by Bdellovibrio bacteriovorus significantly reduces viability and alters the microbial community composition of activated sludge flocs and granules.', FEMS Microbiology Ecology, vol. 93, no. 4.View/Download from: UTS OPUS or Publisher's site
We recently isolated and characterised a predatory Bdellovibrio bacteriovorus strain from activated sludge (Ulu Pandan Water Reclamation Plant, Singapore), and this strain, B. bacteriovorus UP, was able to prey upon a broad spectrum of bacterial isolates from the activated sludge when grown as planktonic cells or as biofilms. Here, we have tested the effect of Bdellovibrio predation on floccular and granular sludge to determine if the spatial organisation, loosely or tightly aggregated communities, was protective from predation. The effect of predation was assessed using a combination of biomass quantification, cellular activity measurement and microscopic image analysis to determine community viability. Additionally, changes in the microbial communities due to predation by B. bacteriovorus UP were analysed through total RNA sequencing. Predation led to a significant reduction in microbial activity and total biomass for both floccular and granular sludge communities. Predation was also associated with significant changes in the microbial community composition in both communities, with >90% of the community members reduced in relative abundance after 24 h. Of those community members, the dominant organisms, such as Proteobacteria and Bacteroidetes, were the most affected phylotypes. This suggests that predatory bacteria, which display indiscriminant feeding, could significantly shift the species composition and thus, may disturb the operational performance of wastewater treatment systems.
Hou, Z, Shankar, YV, Liu, Y, Ding, F, Subramanion, JL, Ravikumar, V, Zamudio-Vázquez, R, Keogh, D, Lim, H, Tay, MYF, Bhattacharjya, S, Rice, SA, Shi, J, Duan, H, Liu, X-W, Mu, Y, Tan, NS, Tam, KC, Pethe, K & Chan-Park, MB 2017, 'Nanoparticles of Short Cationic Peptidopolysaccharide Self-Assembled by Hydrogen Bonding with Antibacterial Effect against Multidrug-Resistant Bacteria.', ACS applied materials & interfaces, vol. 9, no. 44, pp. 38288-38303.View/Download from: UTS OPUS or Publisher's site
Cationic antimicrobial peptides (AMPs) and polymers are active against many multidrug-resistant (MDR) bacteria, but only a limited number of these compounds are in clinical use due to their unselective toxicity. The typical strategy for achieving selective antibacterial efficacy with low mammalian cell toxicity is through balancing the ratio of cationicity to hydrophobicity. Herein, we report a cationic nanoparticle self-assembled from chitosan-graft-oligolysine (CSM5-K5) chains with ultralow molecular weight (1450 Da) that selectively kills bacteria. Further, hydrogen bonding rather than the typical hydrophobic interaction causes the polymer chains to be aggregated together in water into small nanoparticles (with about 37 nm hydrodynamic radius) to concentrate the cationic charge of the lysine. When complexed with bacterial membrane, these cationic nanoparticles synergistically cluster anionic membrane lipids and produce a greater membrane perturbation and antibacterial effect than would be achievable by the same quantity of charge if dispersed in individual copolymer molecules in solution. The small zeta potential (+15 mV) and lack of hydrophobicity of the nanoparticles impedes the insertion of the copolymer into the cell bilayer to improve biocompatibility. In vivo study (using a murine excisional wound model) shows that CSM5-K5 suppresses the growth of methicillin-resistant Staphylococcus aureus (MRSA) bacteria by 4.0 orders of magnitude, an efficacy comparable to that of the last resort MRSA antibiotic vancomycin; it is also noninflammatory with little/no activation of neutrophils (CD11b and Ly6G immune cells). This study demonstrates a promising new class of cationic polymers-short cationic peptidopolysaccharides-that effectively attack MDR bacteria due to the synergistic clustering of, rather than insertion into, bacterial anionic lipids by the concentrated polymers in the resulting hydrogen-bonding-stabilized cationic nanoparticles.
Howlin, RP, Cathie, K, Hall-Stoodley, L, Cornelius, V, Duignan, C, Allan, RN, Fernandez, BO, Barraud, N, Bruce, KD, Jefferies, J, Kelso, M, Kjelleberg, S, Rice, SA, Rogers, GB, Pink, S, Smith, C, Sukhtankar, PS, Salib, R, Legg, J, Carroll, M, Daniels, T, Feelisch, M, Stoodley, P, Clarke, SC, Connett, G, Faust, SN & Webb, JS 2017, 'Low-Dose Nitric Oxide as Targeted Anti-biofilm Adjunctive Therapy to Treat Chronic Pseudomonas aeruginosa Infection in Cystic Fibrosis.', Molecular therapy : the journal of the American Society of Gene Therapy, vol. 25, no. 9, pp. 2104-2116.View/Download from: UTS OPUS or Publisher's site
Despite aggressive antibiotic therapy, bronchopulmonary colonization by Pseudomonas aeruginosa causes persistent morbidity and mortality in cystic fibrosis (CF). Chronic P. aeruginosa infection in the CF lung is associated with structured, antibiotic-tolerant bacterial aggregates known as biofilms. We have demonstrated the effects of non-bactericidal, low-dose nitric oxide (NO), a signaling molecule that induces biofilm dispersal, as a novel adjunctive therapy for P. aeruginosa biofilm infection in CF in an ex vivo model and a proof-of-concept double-blind clinical trial. Submicromolar NO concentrations alone caused disruption of biofilms within ex vivo CF sputum and a statistically significant decrease in ex vivo biofilm tolerance to tobramycin and tobramycin combined with ceftazidime. In the 12-patient randomized clinical trial, 10 ppm NO inhalation caused significant reduction in P. aeruginosa biofilm aggregates compared with placebo across 7 days of treatment. Our results suggest a benefit of using low-dose NO as adjunctive therapy to enhance the efficacy of antibiotics used to treat acute P. aeruginosa exacerbations in CF. Strategies to induce the disruption of biofilms have the potential to overcome biofilm-associated antibiotic tolerance in CF and other biofilm-related diseases.
Huynh, TT, Jamil, I, Pianegonda, NA, Blanksby, SJ, Barker, PJ, Manefield, M & Rice, SA 2017, 'Investigation of the microbial communities colonizing prepainted steel used for roofing and walling.', MicrobiologyOpen, vol. 6, no. 2, pp. 1-11.View/Download from: UTS OPUS or Publisher's site
Microbial colonization of prepainted steel, commonly used in roofing applications, impacts their aesthetics, durability, and functionality. Understanding the relevant organisms and the mechanisms by which colonization occurs would provide valuable information that can be subsequently used to design fouling prevention strategies. Here, next-generation sequencing and microbial community finger printing (T-RFLP) were used to study the community composition of microbes colonizing prepainted steel roofing materials at Burrawang, Australia and Kapar, Malaysia over a 52-week period. Community diversity was low and was dominated by Bacillus spp., cyanobacteria, actinobacteria, Cladosporium sp., Epicoccum nigrum, and Teratosphaeriaceae sp. Cultivation-based methods isolated approximately 20 different fungi and bacteria, some of which, such as E. nigrum and Cladosporium sp., were represented in the community sequence data. Fluorescence in situ hybridization imaging showed that fungi were the most dominant organisms present. Analysis of the sequence and T-RFLP data indicated that the microbial communities differed significantly between locations and changed significantly over time. The study demonstrates the utility of molecular ecology tools to identify and characterize microbial communities associated with the fouling of painted steel surfaces and ultimately can enable the targeted development of control strategies based on the dominant species responsible for fouling.
Karampatzakis, A, Song, CZ, Allsopp, LP, Filloux, A, Rice, SA, Cohen, Y, Wohland, T & Török, P 2017, 'Probing the internal micromechanical properties of Pseudomonas aeruginosa biofilms by Brillouin imaging.', npj Biofilms and Microbiomes, vol. 3, pp. 20-20.View/Download from: UTS OPUS or Publisher's site
Biofilms are organised aggregates of bacteria that adhere to each other or surfaces. The matrix of extracellular polymeric substances that holds the cells together provides the mechanical stability of the biofilm. In this study, we have applied Brillouin microscopy, a technique that is capable of measuring mechanical properties of specimens on a micrometre scale based on the shift in frequency of light incident upon a sample due to thermal fluctuations, to investigate the micromechanical properties of an active, live Pseudomonas aeruginosa biofilm. Using this non-contact and label-free technique, we have extracted information about the internal stiffness of biofilms under continuous flow. No correlation with colony size was found when comparing the averages of Brillouin shifts of two-dimensional cross-sections of randomly selected colonies. However, when focusing on single colonies, we observed two distinct spatial patterns: in smaller colonies, stiffness increased towards their interior, indicating a more compact structure of the centre of the colony, whereas, larger (over 45 μm) colonies were found to have less stiff interiors.
Kundukad, B, Schussman, M, Yang, K, Seviour, T, Yang, L, Rice, SA, Kjelleberg, S & Doyle, PS 2017, 'Mechanistic action of weak acid drugs on biofilms.', Scientific Reports, vol. 7, no. 1, pp. 1-12.View/Download from: UTS OPUS or Publisher's site
Selective permeability of a biofilm matrix to some drugs has resulted in the development of drug tolerant bacteria. Here we studied the efficacy of a weak organic acid drug, N-acetyl-L-cysteine (NAC), on the eradication of biofilms formed by the mucoid strain of Pseudomonas aeruginosa and investigated the commonality of this drug with that of acetic acid. We showed that NAC and acetic acid at pH < pKa can penetrate the matrix and eventually kill 100% of the bacteria embedded in the biofilm. Once the bacteria are killed, the microcolonies swell in size and passively shed bacteria, suggesting that the bacteria act as crosslinkers within the extracellular matrix. Despite shedding of the bacteria, the remnant matrix remains intact and behaves as a pH-responsive hydrogel. These studies not only have implications for drug design but also offer a route to generate robust soft matter materials.
Nair, HAS, Periasamy, S, Yang, L, Kjelleberg, S & Rice, SA 2017, 'Real Time, Spatial, and Temporal Mapping of the Distribution of c-di-GMP during Biofilm Development.', Journal of Biological Chemistry, vol. 292, no. 2, pp. 477-487.View/Download from: UTS OPUS or Publisher's site
Bis-(3'-5')-cyclic dimeric guanosine monophosphate (c-di-GMP) is a dynamic intracellular signaling molecule that plays a central role in the biofilm life cycle. Current methodologies for the quantification of c-di-GMP are typically based on chemical extraction, representing end point measurements. Chemical methodologies also fail to take into consideration the physiological heterogeneity of the biofilm and thus represent an average c-di-GMP concentration across the entire biofilm. To address these problems, a ratiometric, image-based quantification method has been developed based on expression of the green fluorescence protein (GFP) under the control of the c-di-GMP-responsive cdrA promoter (Rybtke, M. T., Borlee, B. R., Murakami, K., Irie, Y., Hentzer, M., Nielsen, T. E., Givskov, M., Parsek, M. R., and Tolker-Nielsen, T. (2012) Appl. Environ. Microbiol. 78, 5060-5069). The methodology uses the cyan fluorescent protein (CFP) as a biomass indicator and the GFP as a c-di-GMP reporter. Thus, the CFP/GFP ratio gives the effective c-di-GMP per biomass. A binary mask was applied to alleviate background fluorescence, and fluorescence was calibrated against known c-di-GMP concentrations. Using flow cells for biofilm formation, c-di-GMP showed a non-uniform distribution across the biofilm, with concentrated hot spots of c-di-GMP. Additionally, c-di-GMP was found to be localized at the outer boundary of mature colonies in contrast to a uniform distribution in early stage, small colonies. These data demonstrate the application of a method for the in situ, real time quantification of c-di-GMP and show that the amount of this biofilm-regulating second messenger was dynamic with time and colony size, reflecting the extent of biofilm heterogeneity in real time.
Oh, H-S, Tan, CH, Low, JH, Rzechowicz, M, Siddiqui, MF, Winters, H, Kjelleberg, S, Fane, AG & Rice, SA 2017, 'Quorum quenching bacteria can be used to inhibit the biofouling of reverse osmosis membranes', Water Research, vol. 112, pp. 29-37.View/Download from: UTS OPUS or Publisher's site
Poh, WH, Barraud, N, Guglielmo, S, Lazzarato, L, Rolando, B, Fruttero, R & Rice, SA 2017, 'Furoxan Nitric Oxide Donors Disperse Pseudomonas aeruginosa Biofilms, Accelerate Growth, and Repress Pyoverdine Production.', ACS Chemical Biology.View/Download from: UTS OPUS or Publisher's site
The use of nitric oxide (NO) as a signal for biofilm dispersal has been shown to increase the susceptibility of many biofilms to antibiotics, promoting their eradication. The delivery of NO to biofilms can be achieved by using NO donors with different kinetics and properties of NO release that can influence their efficacy as biofilm control agents. In this study, the kinetics of three furoxan derivatives were evaluated. The effects of these NO donors, which have an advantageous pharmacological profile of slower onset with an extended duration of action, on Pseudomonas aeruginosa growth, biofilm development, and dispersal were also characterized. Compound LL4254, which showed a fast rate of NO release, induced biofilm dispersal at approximately 200 μM. While LL4212 and LL4216 have a slower rate of NO release, both compounds could induce biofilm dispersal, under the same treatment conditions, when used at higher concentrations. In addition, LL4212 and LL4216 were found to promote P. aeruginosa growth in iron-limited minimal medium, leading to a faster rate of biofilm formation and glucose utilization, and ultimately resulted in early dispersal of biofilm cells through carbon starvation. High concentrations of LL4216 also repressed production of the siderophore pyoverdine by more than 50-fold, via both NOx-dependent and NOx-independent mechanisms. The effects on growth and pyoverdine levels exerted by the furoxans appeared to be mediated by NO-independent mechanisms, suggesting functional activities of furoxans in addition to their release of NO and nitrite. Overall, this study reveals that secondary effects of furoxans are important considerations for their use as NO-releasing dispersal agents and that these compounds could be potentially redesigned as pyoverdine inhibitors.
Pu, Y, Du, Y, Khin, MM, Ravikumar, V, Rice, SA, Duan, H & Chan-Park, MB 2017, 'Using Diphenylphosphoryl Azide (DPPA) for the Facile Synthesis of Biodegradable Antiseptic Random Copolypeptides.', Macromolecular Rapid Communications, vol. 38, no. 7, pp. 1-7.View/Download from: UTS OPUS or Publisher's site
A facile method has been developed for the large-scale synthesis of random copolypeptides composed of multiple (i.e., cationic, hydrophobic, and hydrophilic) amino acids and their relative ratios have been optimized for broad-spectrum antibacterial effect. The copolypeptides obtained have measured compositions close to the design ratios in spite of the differing reactivities of the different amino acids. An optimized random copolypeptide of lysine, leucine, and serine (denoted as KLS-3) mimicking the composition of LL-37 host defense peptide gives broad spectrum antibacterial activity against clinically relevant Gram-negative and Gram-positive bacteria such as methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa (PAO1) with minimum inhibitory concentrations (MICs) of 32-64 μg mL-1 , as well as good MICs against multidrug resistant Gram-negative bacteria of Escherichia coli EC 958 (64 μg mL-1 ) and Klebseilla pneumoniae PTR3 (128 μg mL-1 ). This method can be applied to the facile large-scale copolymerization of multiple amino acids, including unnatural amino acids, to make effective antibacterial copolypeptides.
Tan, CH, Lee, KWK, Burmolle, M, Kjelleberg, S & Rice, SA 2017, 'All together now: experimental multispecies biofilm model systems', ENVIRONMENTAL MICROBIOLOGY, vol. 19, no. 1, pp. 42-53.View/Download from: UTS OPUS or Publisher's site
Liu, S, Gunawan, C, Barraud, N, Rice, SA, Harry, EJ & Amal, R 2016, 'Understanding, Monitoring, and Controlling Biofilm Growth inDrinking Water Distribution Systems', Environmental Science and Technology (Washington), vol. 50, pp. 8954-8976.View/Download from: UTS OPUS or Publisher's site
In drinking water distribution systems (DWDS), biofilms are the predominant mode of microbial growth, with the presence of extracellular polymeric substance (EPS) protecting the biomass from environmental and shear stresses. Biofilm formation poses a significant problem to the drinking water industry as a potential source of bacterial contamination, including pathogens, and, in many cases, also affecting the taste and odor of drinking water and promoting the corrosion of pipes. This article critically reviews important research findings on biofilm growth in DWDS, examining the factors affecting their formation and characteristics as well as the various technologies to characterize and monitor and, ultimately, to control their growth. Research indicates that temperature fluctuations potentially affect not only the initial bacteria-to-surface attachment but also the growth rates of biofilms. For the latter, the effect is unique for each type of biofilm-forming bacteria; ammonia-oxidizing bacteria, for example, grow more-developed biofilms at a typical summer temperature of 22 °C compared to 12 °C in fall, and the opposite occurs for the pathogenic Vibrio cholerae. Recent investigations have found the formation of thinner yet denser biofilms under high and turbulent flow regimes of drinking water, in comparison to the more porous and loosely attached biofilms at low flow rates. Furthermore, in addition to the rather well-known tendency of significant biofilm growth on corrosion-prone metal pipes, research efforts also found leaching of growth-promoting organic compounds from the increasingly popular use of polymer-based pipes. Knowledge of the unique microbial members of drinking water biofilms and, importantly, the influence of water characteristics and operational conditions on their growth can be applied to optimize various operational parameters to minimize biofilm accumulation. More-detailed characterizations of the biofilm population size and structure are now...
Alqarni, B, Colley, B, Klebensberger, J, McDougald, D & Rice, SA 2016, 'Expression stability of 13 housekeeping genes during carbon starvation of Pseudomonas aeruginosa', JOURNAL OF MICROBIOLOGICAL METHODS, vol. 127, pp. 182-187.View/Download from: UTS OPUS or Publisher's site
Chew, SC, Kundukad, B, Teh, WK, Doyle, P, Yang, L, Rice, SA & Kjelleberg, S 2016, 'Mechanical signatures of microbial biofilms in micropillar-embedded growth chambers', SOFT MATTER, vol. 12, no. 23, pp. 5224-5232.View/Download from: UTS OPUS or Publisher's site
Colley, B, Dederer, V, Carnell, M, Kjelleberg, S, Rice, SA & Klebensberger, J 2016, 'SiaA/D Interconnects c-di-GMP and RsmA Signaling to Coordinate Cellular Aggregation of Pseudomonas aeruginosa in Response to Environmental Conditions', FRONTIERS IN MICROBIOLOGY, vol. 7.View/Download from: UTS OPUS or Publisher's site
Feng, S, Tan, CH, Cohen, Y & Rice, SA 2016, 'Isolation of Bdellovibrio bacteriovorus from a tropical wastewater treatment plant and predation of mixed species biofilms assembled by the native community members', Environmental Microbiology, vol. 18, no. 11, pp. 3923-3931.View/Download from: UTS OPUS or Publisher's site
© 2016 Society for Applied Microbiology and John Wiley & Sons Ltd.It is reported here that a predatory bacterium belonging to the Genus Bdellovibrio, was isolated from activated sludge at the Ulu Pandan Water Reclamation Plant, Singapore. 16S rDNA gene sequencing analysis revealed that this isolate was 99% identical to 'Bdellovibrio bacteriovorus strain Tiberius' and hence is designated as 'Bdellovibrio bacteriovorus UP'. Using a novel approach based on fluorescence in situ hybridization (FISH), a prey cell density-dependent growth pattern of B. bacteriovorus UP was established. B. bacteriovorus UP preyed upon a broad range of bacterial species (60 species) isolated from the activated sludge. Except for Ochrobactrum anthropi, all Gram-negative species were sensitive to predation by B. bacteriovorus UP irrespective of the mode of growth (planktonic or biofilm). Similarly, the predation-sensitive species were not protected by the predation-resistant species, O. anthropi, as determined in multiple dual-species planktonic and biofilm consortia. Given the broad prey spectrum, B. bacteriovorus UP may impact functional community members, which are largely members of the Proteobacteria. Thus, these results provide an important insight to the role of predatory bacteria in shaping of community structure and function in both natural and engineered ecosystems.
Flemming, H-C, Wingender, J, Szewzyk, U, Steinberg, P, Rice, SA & Kjelleberg, S 2016, 'Biofilms: an emergent form of bacterial life', NATURE REVIEWS MICROBIOLOGY, vol. 14, no. 9, pp. 563-575.View/Download from: UTS OPUS or Publisher's site
Ho, JS, Low, JH, Sim, LN, Webster, RD, Rice, SA, Fane, AG & Coster, HGL 2016, 'In-situ monitoring of biofouling on reverse osmosis membranes: Detection and mechanistic study using electrical impedance spectroscopy', JOURNAL OF MEMBRANE SCIENCE, vol. 518, pp. 229-242.View/Download from: UTS OPUS or Publisher's site
Kundukad, B, Seviour, T, Liang, Y, Rice, SA, Kjelleberg, S & Doyle, PS 2016, 'Mechanical properties of the superficial biofilm layer determine the architecture of biofilms', SOFT MATTER, vol. 12, no. 26, pp. 5718-5726.View/Download from: UTS OPUS or Publisher's site
Lee, KWK, Yam, JKH, Mukherjee, M, Periasamy, S, Steinberg, PD, Kjelleberg, S & Rice, SA 2016, 'Interspecific diversity reduces and functionally substitutes for intraspecific variation in biofilm communities', ISME JOURNAL, vol. 10, no. 4, pp. 846-857.View/Download from: UTS OPUS or Publisher's site
Nguyen, T-K, Selvanayagam, R, Ho, KKK, Chen, R, Kutty, SK, Rice, SA, Kumar, N, Barraud, N, Duong, HTT & Boyer, C 2016, 'Co-delivery of nitric oxide and antibiotic using polymeric nanoparticles', CHEMICAL SCIENCE, vol. 7, no. 2, pp. 1016-1027.View/Download from: Publisher's site
Nizalapur, S, Kimyon, O, Biswas, NN, Gardner, CR, Griffith, R, Rice, SA, Manefield, M, Willcox, M, Black, DS & Kumar, N 2016, 'Design, synthesis and evaluation of N-aryl-glyoxamide derivatives as structurally novel bacterial quorum sensing inhibitors', ORGANIC & BIOMOLECULAR CHEMISTRY, vol. 14, no. 2, pp. 680-693.View/Download from: UTS OPUS or Publisher's site
Paine, MRL, Pianegonda, NA, Huynh, TT, Manefield, M, MacLaughlin, SA, Rice, SA, Barker, PJ & Blanksby, SJ 2016, 'Evaluation of hindered amine light stabilisers and their N-chlorinated derivatives as antibacterial and antifungal additives for thermoset surface coatings', PROGRESS IN ORGANIC COATINGS, vol. 99, pp. 330-336.View/Download from: UTS OPUS or Publisher's site
Rice, SA, Wuertz, S & Kjelleberg, S 2016, 'Next-generation studies of microbial biofilm communities', MICROBIAL BIOTECHNOLOGY, vol. 9, no. 5, pp. 677-680.View/Download from: UTS OPUS or Publisher's site
Wang, W, Zhou, QT, Sun, S-P, Denman, JA, Gengenbach, TR, Barraud, N, Rice, SA, Li, J, Yang, M & Chan, H-K 2016, 'Effects of Surface Composition on the Aerosolisation and Dissolution of Inhaled Antibiotic Combination Powders Consisting of Colistin and Rifampicin', AAPS JOURNAL, vol. 18, no. 2, pp. 372-384.View/Download from: UTS OPUS or Publisher's site
Wong, EHH, Khin, MM, Ravikumar, V, Si, Z, Rice, SA & Chan-Park, MB 2016, 'Modulating Antimicrobial Activity and Mammalian Cell Biocompatibility with Glucosamine-Functionalized Star Polymers', BIOMACROMOLECULES, vol. 17, no. 3, pp. 1170-1178.View/Download from: UTS OPUS or Publisher's site
Jeong, S, Cho, K, Bae, H, Keshvardoust, P, Rice, SA, Vigneswaran, S, Lee, S & Leiknes, T 2016, 'Effect of microbial community structure on organic removal and biofouling in membrane adsorption bioreactor used in seawater pretreatment', CHEMICAL ENGINEERING JOURNAL, vol. 294, pp. 30-39.View/Download from: Publisher's site
Lee, BSB, Toh, S-L, Ryan, S, Simpson, JM, Clezy, K, Bossa, L, Rice, S, Marial, O, Weber, G, Kaur, J, Boswell-Ruys, C, Goodall, S, Middleton, J, Tuderhope, M & Kotsiou, G 2016, 'Probiotics (LGG-BB12 or RC14-GR1) versus placebo as prophylaxis for urinary tract infection in persons with spinal cord injury (ProSCIUTTU): a study protocol for a randomised controlled trial', BMC Urology, vol. 16:18.View/Download from: UTS OPUS or Publisher's site
Luo, J, Zhang, J, Barnes, RJ, Tan, X, McDougald, D, Fane, AG, Zhuang, G, Kjelleberg, S, Cohen, Y & Rice, SA 2015, 'The application of nitric oxide to control biofouling of membrane bioreactors', MICROBIAL BIOTECHNOLOGY, vol. 8, no. 3, pp. 549-560.View/Download from: UTS OPUS or Publisher's site
Luo, J, Zhang, J, Tan, X, McDougald, D, Zhuang, G, Fane, AG, Kjelleberg, S, Cohen, Y & Rice, SA 2015, 'Characterization of the archaeal community fouling a membrane bioreactor.', Journal of Environmental Sciences, vol. 29, pp. 115-123.View/Download from: UTS OPUS or Publisher's site
Biofilm formation, one of the primary causes of biofouling, results in reduced membrane flux or increased transmembrane pressure and thus represents a major impediment to the wider implementation of membrane bioreactor (MBR) technologies for water purification. Most studies have focused on the role of bacteria in membrane fouling as they are the most dominant and best studied organisms present in the MBR. In contrast, there is limited information on the role of the archaeal community in biofilm formation in MBRs. This study investigated the composition of the archaeal community during the process of biofouling in an MBR. The archaeal community was observed to have lower richness and diversity in the biofilm than the sludge during the establishment of biofilms at low transmembrane pressure (TMP). Clustering of the communities based on the Bray-Curtis similarity matrix indicated that a subset of the sludge archaeal community formed the initial biofilms. The archaeal community in the biofilm was mainly composed of Thermoprotei, Thermoplasmata, Thermococci, Methanopyri, Methanomicrobia and Halobacteria. Among them, the Thermoprotei and Thermoplasmata were present at higher relative proportions in the biofilms than they were in the sludge. Additionally, the Thermoprotei, Thermoplasmata and Thermococci were the dominant organisms detected in the initial biofilms at low TMP, while as the TMP increased, the Methanopyri, Methanomicrobia, Aciduliprofundum and Halobacteria were present at higher abundances in the biofilms at high TMP.
Mai-Prochnow, A, Hui, JGK, Kjelleberg, S, Rakonjac, J, McDougald, D & Rice, SA 2015, ''Big things in small packages: the genetics of filamentous phage and effects on fitness of their host'', FEMS MICROBIOLOGY REVIEWS, vol. 39, no. 4, pp. 465-487.View/Download from: UTS OPUS or Publisher's site
Sun, S, Tay, QXM, Kjelleberg, S, Rice, SA & McDougald, D 2015, 'Quorum sensing-regulated chitin metabolism provides grazing resistance to Vibrio cholerae biofilms', ISME JOURNAL, vol. 9, no. 8, pp. 1812-1820.View/Download from: UTS OPUS or Publisher's site
Zhang, Q, Shuwen, G, Zhang, J, Fane, AG, Kjelleberg, S, Rice, SA & McDougald, D 2015, 'Analysis of microbial community composition in a lab-scale membrane distillation bioreactor', JOURNAL OF APPLIED MICROBIOLOGY, vol. 118, no. 4, pp. 940-953.View/Download from: UTS OPUS or Publisher's site
Barnes, RJ, Low, JH, Bandi, RR, Tay, M, Chua, F, Aung, T, Fane, AG, Kjelleberg, S & Rice, SA 2015, 'Nitric Oxide Treatment for the Control of Reverse Osmosis Membrane Biofouling', APPLIED AND ENVIRONMENTAL MICROBIOLOGY, vol. 81, no. 7, pp. 2515-2524.View/Download from: Publisher's site
Barraud, N, Kelso, MJ, Rice, SA & Kjelleberg, S 2015, 'Nitric Oxide: A Key Mediator of Biofilm Dispersal with Applications in Infectious Diseases', CURRENT PHARMACEUTICAL DESIGN, vol. 21, no. 1, pp. 31-42.
© 2015 American Society for Microbiology. All rights reserved. One common feature of biofilm development is the active dispersal of cells from the mature biofilm, which completes the biofilm life cycle and allows for the subsequent colonization of new habitats. Dispersal is likely to be critical for species survival and appears to be a precisely regulated process that involves a complex network of genes and signal transduction systems. Sophisticated molecular mechanisms control the transition of sessile biofilm cells into dispersal cells and their coordinated detachment and release in the bulk liquid. Dispersal cells appear to be specialized and exhibit a unique phenotype different from biofilm or planktonic bacteria. Further, the dispersal population is characterized by a high level of heterogeneity, reminiscent of, but distinct from, that in the biofilm, which could potentially allow for improved colonization under various environmental conditions. Here we review recent advances in characterizing the molecular mechanisms that regulate biofilm dispersal events and the impact of dispersal in a broader ecological context. Several strategies that exploit the mechanisms controlling biofilm dispersal to develop as applications for biofilm control are also presented.
Biswas, NN, Kutty, SK, Barraud, N, Iskander, GM, Griffith, R, Rice, SA, Willcox, M, Black, DS & Kumar, N 2015, 'Indole-based novel small molecules for the modulation of bacterial signalling pathways', ORGANIC & BIOMOLECULAR CHEMISTRY, vol. 13, no. 3, pp. 925-937.View/Download from: Publisher's site
Chew, SC, Rice, SA, Kjelleberg, S & Yang, L 2015, 'In Situ Mapping of the Mechanical Properties of Biofilms by Particle-tracking Microrheology', JOVE-JOURNAL OF VISUALIZED EXPERIMENTS, no. 106.View/Download from: Publisher's site
Goh, W-K, Gardner, CR, Sekhar, KVGC, Biswas, NN, Nizalapur, S, Rice, SA, Willcox, M, Black, DS & Kumar, N 2015, 'Synthesis, quorum sensing inhibition and docking studies of 1,5-dihydropyrrol-2-ones', BIOORGANIC & MEDICINAL CHEMISTRY, vol. 23, no. 23, pp. 7366-7377.View/Download from: Publisher's site
Kutty, SK, Barraud, N, Ho, KKK, Iskander, GM, Griffith, R, Rice, SA, Bhadbhade, M, Willcox, MDP, Blacka, DS & Kumar, N 2015, 'Hybrids of acylated homoserine lactone and nitric oxide donors as inhibitors of quorum sensing and virulence factors in Pseudomonas aeruginosa', ORGANIC & BIOMOLECULAR CHEMISTRY, vol. 13, no. 38, pp. 9850-9861.View/Download from: Publisher's site
Lafleur, JE & Rice, SA 2015, 'Induction of resistance to S-aureus in an environmental marine biofilm grown in Sydney Harbor, NSW, Australia', WORLD JOURNAL OF MICROBIOLOGY & BIOTECHNOLOGY, vol. 31, no. 2, pp. 353-358.View/Download from: Publisher's site
Liu, T, Yu, Y-Y, Deng, X-P, Ng, CK, Cao, B, Wang, J-Y, Rice, SA, Kjelleberg, S & Song, H 2015, 'Enhanced Shewanella biofilm promotes bioelectricity generation', BIOTECHNOLOGY AND BIOENGINEERING, vol. 112, no. 10, pp. 2051-2059.View/Download from: Publisher's site
Periasamy, S, Nair, HAS, Lee, KWK, Ong, J, Goh, JQJ, Kjelleberg, S & Rice, SA 2015, 'Pseudomonas aeruginosa PA01 exopolysaccharides are important for mixed species biofilm community development and stress tolerance', FRONTIERS IN MICROBIOLOGY, vol. 6.View/Download from: Publisher's site
Roser, DJ, Van Den Akker, B, Boase, S, Haas, CN, Ashbolt, NJ & Rice, SA 2015, 'Dose-response algorithms for water-borne Pseudomonas aeruginosa folliculitis', EPIDEMIOLOGY AND INFECTION, vol. 143, no. 7, pp. 1524-1537.View/Download from: Publisher's site
Seviour, T, Doyle, LE, Lauw, SJL, Hinks, J, Rice, SA, Nesatyy, VJ, Webster, RD, Kjelleberg, S & Marsili, E 2015, 'Voltammetric profiling of redox-active metabolites expressed by Pseudomonas aeruginosa for diagnostic purposes', CHEMICAL COMMUNICATIONS, vol. 51, no. 18, pp. 3789-3792.View/Download from: Publisher's site
Seviour, T, Weerachanchai, P, Hinks, J, Roizman, D, Rice, SA, Bai, L, Lee, J-M & Kjelleberg, S 2015, 'Solvent optimization for bacterial extracellular matrices: a solution for the insoluble', RSC ADVANCES, vol. 5, no. 10, pp. 7469-7478.View/Download from: Publisher's site
Sule, N, Rice, SA, Gray, SK & Scherer, NF 2015, 'An electrodynamics-Langevin dynamics (ED-LD) approach to simulate metal nanoparticle interactions and motion', OPTICS EXPRESS, vol. 23, no. 23, pp. 29978-29992.View/Download from: Publisher's site
Tan, CH, Koh, KS, Xie, C, Zhang, J, Tan, XH, Lee, GP, Zhou, Y, Ng, WJ, Rice, SA & Kjelleberg, S 2015, 'Community quorum sensing signalling and quenching: microbial granular biofilm assembly', NPJ BIOFILMS AND MICROBIOMES, vol. 1.View/Download from: Publisher's site
Yang, Y, Ding, Y, Hu, Y, Cao, B, Rice, SA, Kjelleberg, S & Song, H 2015, 'Enhancing Bidirectional Electron Transfer of Shewanella oneidensis by a Synthetic Flavin Pathway', ACS SYNTHETIC BIOLOGY, vol. 4, no. 7, pp. 815-823.View/Download from: Publisher's site
Zhou, QT, Sun, S-P, Chan, JGY, Wang, P, Barraud, N, Rice, SA, Wang, J, Li, J & Chan, H-K 2015, 'Novel Inhaled Combination Powder Containing Amorphous Colistin and Crystalline Rifapentine with Enhanced Antimicrobial Activities against Planktonic Cells and Biofilm of Pseudomonas aeruginosa for Respiratory Infections', MOLECULAR PHARMACEUTICS, vol. 12, no. 8, pp. 2594-2603.View/Download from: Publisher's site
Hui, JG, Mai-Prochnow, A, Kjelleberg, S, McDougald, D & Rice, SA 2014, 'Environmental cues and genes involved in establishment of the superinfective Pf4 phage of Pseudomonas aeruginosa.', Frontiers in Microbiology, vol. 5, pp. 1-8.View/Download from: UTS OPUS or Publisher's site
Biofilm development in Pseudomonas aeruginosa is in part dependent on a filamentous phage, Pf4, which contributes to biofilm maturation, cell death, dispersal and variant formation, e.g., small colony variants (SCVs). These biofilm phenotypes correlate with the conversion of the Pf4 phage into a superinfection (SI) variant that reinfects and kills the prophage carrying host, in contrast to other filamentous phage that normally replicate without killing their host. Here we have investigated the physiological cues and genes that may be responsible for this conversion. Flow through biofilms typically developed SI phage approximately days 4 or 5 of development and corresponded with dispersal. Starvation for carbon or nitrogen did not lead to the development of SI phage. In contrast, exposure of the biofilm to nitric oxide, H2O2 or the DNA damaging agent, mitomycin C, showed a trend of increased numbers of SI phage, suggesting that reactive oxygen or nitrogen species (RONS) played a role in the formation of SI phage. In support of this, mutation of oxyR, the major oxidative stress regulator in P. aeruginosa, resulted in higher level of and earlier superinfection compared to the wild-type (WT). Similarly, inactivation of mutS, a DNA mismatch repair gene, resulted in the early appearance of the SI phage and this was four log higher than the WT. In contrast, loss of recA, which is important for DNA repair and the SOS response, also resulted in a delayed and decreased production of SI phage. Treatments or mutations that increased superinfection also correlated with an increase in the production of morphotypic variants. The results suggest that the accumulation of RONS by the biofilm may result in DNA lesions in the Pf4 phage, leading to the formation of SI phage, which subsequently selects for morphotypic variants, such as SCVs.
Luo, J, Zhang, J, Tan, X, McDougald, SD, Zhuang, G, Fane, AG, Kjelleberg, S, Cohen, Y & Rice, SA 2014, 'The correlation between biofilm biopolymer composition and membrane fouling in submerged membrane bioreactors', Biofouling, vol. 30, no. 9, pp. 1093-1110.View/Download from: UTS OPUS or Publisher's site
Biofouling, the combined effect of microorganism and biopolymer accumulation, significantly reduces the process efficiency of membrane bioreactors (MBRs). Here, four biofilm components, alpha-polysaccharides, beta-polysaccharides, proteins and microorganisms, were quantified in MBRs. The biomass of each component was positively correlated with the transmembrane pressure increase in MBRs. Proteins were the most abundant biopolymer in biofilms and showed the fastest rate of increase. The spatial distribution and co-localization analysis of the biofouling components indicated at least 60% of the extracellular polysaccharide (EPS) components were associated with the microbial cells when the transmembrane pressure (TMP) entered the jump phase, suggesting that the EPS components were either secreted by the biofilm cells or that the deposition of these components facilitated biofilm formation. It is suggested that biofilm formation and the accumulation of EPS are intrinsically coupled, resulting in biofouling and loss of system performance. Therefore, strategies that control biofilm formation on membranes may result in a significant improvement of MBR performance.
Suwarno, SR, Chen, X, Chong, TH, McDougald, D, Cohen, Y, Rice, SA & Fane, AG 2014, 'Biofouling in reverse osmosis processes: The roles of flux, crossflow velocity and concentration polarization in biofilm development', Journal of Membrane Science, vol. 467, pp. 116-125.View/Download from: UTS OPUS or Publisher's site
Biofilm development in a spacer-filled reverse osmosis membrane channel can influence both trans-membrane pressure (TMP) and channel pressure drop (δP CH ). While current pretreatment methods are unable to completely tackle the biofouling problem, more insights are required to provide strategies to minimize the problem. This study examined the role of operating parameters (i.e. flux and crossflow velocity) to minimize biofouling in RO processes. The experiments were conducted with a lab-scale high pressure flat sheet RO reactor where changes in pressure drop along the channel and across the membrane were measured. The impact of biofouling was measured at constant fluxes, where the TMP rise and δP CH rise and the biofoulant was quantified as biovolumes of live and dead bacteria on autopsied membrane and spacer samples by confocal laser scanning microscopy (CLSM).The results show that TMP rise increased exponentially with increasing flux, and decreased with increasing crossflow velocity. The channel pressure drop, δP CH , increased when either flux or crossflow velocity was increased, and was more dependent on crossflow. The biofoulant volume on the membrane increased with flux and was less dependent on crossflow. The biofoulant associated with the spacer was much less than on the membrane and relatively insensitive to flux or crossflow velocity.The TMP rise could be correlated with the estimated concentration of nutrient at the membrane surface, C w,N , highlighting the combined roles of flux and crossflow velocity in solute concentration polarization. Previous TMP rise data could also be correlated to the estimated C w,N values. This observation suggests a biofouling mitigation strategy by controlling both incoming nutrient concentration and operating conditions (flux and crossflow). © 2014 Elsevier B.V.
Zhang, Q, Jie, YW, Loong, WL, Zhang, J, Fane, AG, Kjelleberg, S, Rice, SA & McDougald, D 2014, 'Characterization of biofouling in a lab-scale forward osmosis membrane bioreactor (FOMBR).', Water Research, vol. 58, pp. 141-151.View/Download from: UTS OPUS or Publisher's site
Forward osmosis membrane bioreactors (FOMBR) provide high quality permeate, however the propensity for membrane biofouling in FOMBRs is unknown. Here, FOMBRs were operated under high and low aeration and the membrane-associated biofilms were characterized by confocal laser scanning microscopy (CLSM) and rRNA gene-tagged pyrosequencing. CLSM images revealed that there was little biofilm formed under high aeration, while thick biofilms were observed on the membranes operated under low aeration. The diversity and richness of bacterial and archaeal communities as assessed by pyrosequencing varied under high and low aeration. The composition of the bacterial suspended sludge communities and the sessile biomass on the membrane surface, as assessed by non-metric multidimensional scaling, was significantly different under high aeration, but was more similar under low aeration. SIMPER analysis indicated that Pseudomonas, Aeromonas and Fluviicola preferentially attached to the membrane. The results presented here provide a comprehensive understanding of membrane biofouling in FOMBRs, which is essential for the development of effective control strategies.
Barnes, RJ, Bandi, RR, Chua, F, Low, JH, Aung, T, Barraud, N, Fane, AG, Kjelleberg, S & Rice, SA 2014, 'The roles of Pseudomonas aeruginosa extracellular polysaccharides in biofouling of reverse osmosis membranes and nitric oxide induced dispersal', JOURNAL OF MEMBRANE SCIENCE, vol. 466, pp. 161-172.View/Download from: Publisher's site
Chew, SC, Kundukad, B, Seviour, T, van der Maarel, JRC, Yang, L, Rice, SA, Doyle, P & Kjelleberg, S 2014, 'Dynamic Remodeling of Microbial Biofilms by Functionally Distinct Exopolysaccharides', MBIO, vol. 5, no. 4.View/Download from: Publisher's site
Ho, KKK, Chen, R, Willcox, MDP, Rice, SA, Cole, N, Iskander, G & Kumar, N 2014, 'Quorum sensing inhibitory activities of surface immobilized antibacterial dihydropyrrolones via click chemistry', BIOMATERIALS, vol. 35, no. 7, pp. 2336-2345.View/Download from: UTS OPUS or Publisher's site
Lee, KWK, Periasamy, S, Mukherjee, M, Xie, C, Kjelleberg, S & Rice, SA 2014, 'Biofilm development and enhanced stress resistance of a model, mixed-species community biofilm', ISME JOURNAL, vol. 8, no. 4, pp. 894-907.View/Download from: Publisher's site
McElroy, KE, Hui, JGK, Woo, JKK, Luk, AWS, Webb, JS, Kjelleberg, S, Rice, SA & Thomas, T 2014, 'Strain-specific parallel evolution drives short-term diversification during Pseudomonas aeruginosa biofilm formation', PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, vol. 111, no. 14, pp. E1419-E1427.View/Download from: Publisher's site
Roser, DJ, Van den Akker, B, Boase, S, Haas, CN, Ashbolt, NJ & Rice, SA 2014, 'Pseudomonas aeruginosa dose response and bathing water infection', EPIDEMIOLOGY AND INFECTION, vol. 142, no. 3, pp. 449-462.View/Download from: Publisher's site
Tan, CH, Koh, KS, Xie, C, Tay, M, Zhou, Y, Williams, R, Ng, WJ, Rice, SA & Kjelleberg, S 2014, 'The role of quorum sensing signalling in EPS production and the assembly of a sludge community into aerobic granules', ISME JOURNAL, vol. 8, no. 6, pp. 1186-1197.View/Download from: Publisher's site
Jeong, S, Rice, S & Vigneswaran, S 2014, 'Long-term effect on membrane fouling in a new membrane bioreactor as a pretreatment to seawater desalination', Bioresource Technology, vol. 165, pp. 60-68.View/Download from: UTS OPUS or Publisher's site
Barnes, RJ, Bandi, RR, Wong, WS, Barraud, N, McDougald, D, Fane, A, Kjelleberg, S & Rice, SA 2013, 'Optimal dosing regimen of nitric oxide donor compounds for the reduction of Pseudomonas aeruginosa biofilm and isolates from wastewater membranes', BIOFOULING, vol. 29, no. 2, pp. 203-212.View/Download from: UTS OPUS or Publisher's site
Chen, X, Suwarno, SR, Chong, TH, McDougald, D, Kjelleberg, S, Cohen, Y, Fane, AG & Rice, SA 2013, 'Dynamics of biofilm formation under different nutrient levels and the effect on biofouling of a reverse osmosis membrane system', BIOFOULING, vol. 29, no. 3, pp. 319-330.View/Download from: UTS OPUS or Publisher's site
Barraud, N, Buson, A, Jarolimek, W & Rice, SA 2013, 'Mannitol Enhances Antibiotic Sensitivity of Persister Bacteria in Pseudomonas aeruginosa Biofilms', PLOS ONE, vol. 8, no. 12.View/Download from: Publisher's site
Chua, SL, Tan, SY-Y, Rybtke, MT, Chen, Y, Rice, SA, Kjelleberg, S, Tolker-Nielsen, T, Yang, L & Givskov, M 2013, 'Bis-(3 '-5 ')-Cyclic Dimeric GMP Regulates Antimicrobial Peptide Resistance in Pseudomonas aeruginosa', ANTIMICROBIAL AGENTS AND CHEMOTHERAPY, vol. 57, no. 5, pp. 2066-2075.View/Download from: Publisher's site
Kutty, SK, Barraud, N, Pham, A, Iskander, G, Rice, SA, Black, DS & Kumar, N 2013, 'Design, Synthesis, and Evaluation of Firnbrolide-Nitric Oxide Donor Hybrids as Antimicrobial Agents', JOURNAL OF MEDICINAL CHEMISTRY, vol. 56, no. 23, pp. 9517-9529.View/Download from: Publisher's site
Lee, KWK, Arumugam, K, Purbojati, RW, Tay, QXM, Williams, RBH, Kjelleberg, S & Rice, SA 2013, 'Draft genome sequence of Klebsiella pneumoniae strain KP-1', Genome Announcements, vol. 1, no. 6.View/Download from: Publisher's site
© 2013 Lee et al. Klebsiella pneumoniae is ubiquitous in the environment and is a member of a three-species biofilm model. We compared the genome sequence of an environmental isolate, K. pneumoniae strain KP-1, to those of two clinical strains (NTUH-K2044 and MGH 78578). KP-1 possesses strain-specific prophage sequences that distinguish it from the clinical strains.
Tan, SY-Y, Chua, S-L, Chen, Y, Rice, SA, Kjelleberg, S, Nielsen, TE, Yang, L & Givskov, M 2013, 'Identification of Five Structurally Unrelated Quorum-Sensing Inhibitors of Pseudomonas aeruginosa from a Natural-Derivative Database', ANTIMICROBIAL AGENTS AND CHEMOTHERAPY, vol. 57, no. 11, pp. 5629-5641.View/Download from: Publisher's site
Woo, JKK, McElroy, K, Rice, SA, Kirov, SM, Thomas, T & Kjelleberg, S 2013, 'Draft genome sequence of the chronic, nonclonal cystic fibrosis isolate Pseudomonas aeruginosa strain 18A', Genome Announcements, vol. 1, no. 2.View/Download from: Publisher's site
© 2013 Woo et al. Pseudomonas aeruginosa strain 18A is a clinical, nonclonal isolate retrieved from the sputum of a chronically infected cystic fibrosis patient. The genome of 18A was sequenced for comparison with environmental and clinical isolates to identify genes that might facilitate its persistence during infection.
Yepuri, N, Barraud, N, Shah Mohammadi, N, Kardak, B, Kjelleberg, S, Rice, S & Kelso, M 2013, 'Synthesis of cephalosporin-3ˊ-diazeniumdiolates:biofilm dispersing NO-donor prodrug activated by β-lactamase.', Cemical Communication, vol. 49, pp. 4791-4793.
Use of biofilm dispersing NO-donor compounds in combinationwith antibiotics has emerged as a promising new strategy fortreating drug-resistant bacterial biofilm infections.This paper detailsthe synthesis and preliminary evaluation of six cephalosporin-30-diazeniumdiolates as biofilm-targeted NO-donor prodrugs. Eachof the compounds is shown to selectively release NO followingreaction with the bacteria-specific enzymeb-lactamas and totrigger dispersion ofPseudomonas aeruginosa biofilmsin vitro.
Danasamy, G, Jeong, S, Vigneswaran, S & Rice, SA 2013, 'Microbial activity in biofilter used as a pretreatment for seawater desalination', Desalination, vol. 309, pp. 254-260.View/Download from: UTS OPUS or Publisher's site
Biofilters as a pretreatment process in seawater desalination can reduce biofoulants through adsorption and biodegradation. In this study, the performance of granular activated carbon (GAC) biofilter with three different filtration velocities was studied in terms of dissolved organic carbon (DOC) removal. This apart, the microbial activities in the biofilters were measured in terms of concentration of active biomass (adenosine tri-phosphate; ATP) and total cell count. Biofouling potential in biofilter effluents were assessed in terms of transparent exopolymer particles (TEP) and assimilable organic carbon (AOC) concentration. AOC was carried out using a new rapid bioluminescence method. Upon reaching mature stage, the GAC biofilters achieved high DOC removal efficiency of more than 60%, especially the low molecular weight organics. This organic removal was mostly attributed to active biomass on the GAC media. In addition, GAC biofilters led to significant reduction of the AOC and TEP concentration amounting to only 0.6 ± 0.2 µg-C glucose/L and 5.3 ± 1.1 µg-C/L, respectively in effluents. Thus, GAC biofilter is an effective pretreatment in reducing biofouling potential
Jeong, S, Danasamy, G, Vigneswaran, S, Ma, CH & Rice, SA 2013, 'A rapid bioluminescence-based test of assimilable organic carbon for seawater', Desalination, vol. 317, pp. 160-165.View/Download from: UTS OPUS or Publisher's site
The accumulation of biological materials and bacteria on water purification membranes, termed biofouling, is associated with decreased membrane performance and increased cost of operation. One strategy to minimize biofouling is pretreatment of the influent water. In this regard, tools and indicators that can assess the influent water are required, enabling an optimum selection of pretreatment methods. One parameter directly linked to biofouling potential is the concentration of assimilable organic carbon (AOC) in the feed-water. High AOC levels are associated with increased growth potential of the microbial fouling community. This work focused on the development of a new method for rapid and accurate quantification of AOC concentration in seawater. The method is based on the quantification of the bioluminescence response of the marine bacterium Vibrio fischeri MJ-1. Compared to previous methods, this new V. fischeri method was rapid (within 1 h), sensitive (detection limit = 0.1 µg-C glucose equivalents/L) and highly suitable for seawater samples. V. fischeri method was evaluated using real seawater samples. The results showed positive reproductive AOC values. The new V. fischeri AOC method developed has a highly promising potential to be practically adopted as a rapid indicator of AOC concentration and hence biofouling potential of influent marine water.
Fagerlind, MG, Webb, JS, Barraud, N, McDougald, D, Jansson, A, Nilsson, P, Harlen, M, Kjelleberg, S & Rice, SA 2012, 'Dynamic modelling of cell death during biofilm development', JOURNAL OF THEORETICAL BIOLOGY, vol. 295, pp. 23-36.View/Download from: UTS OPUS or Publisher's site
Huynh, TT, McDougald, D, Klebensberger, J, Al Qarni, B, Barraud, N, Rice, SA, Kjelleberg, S & Schleheck, D 2012, 'Glucose Starvation-Induced Dispersal of Pseudomonas aeruginosa Biofilms Is cAMP and Energy Dependent', PLOS ONE, vol. 7, no. 8.View/Download from: UTS OPUS or Publisher's site
McDougald, D, Rice, SA, Barraud, N, Steinberg, PD & Kjelleberg, S 2012, 'Should we stay or should we go: mechanisms and ecological consequences for biofilm dispersal', NATURE REVIEWS MICROBIOLOGY, vol. 10, no. 1, pp. 39-50.View/Download from: UTS OPUS or Publisher's site
Suwarno, SR, Chen, X, Chong, TH, Puspitasari, VL, McDougald, D, Cohen, Y, Rice, SA & Fane, AG 2012, 'The impact of flux and spacers on biofilm development on reverse osmosis membranes', JOURNAL OF MEMBRANE SCIENCE, vol. 405, pp. 219-232.View/Download from: UTS OPUS or Publisher's site
Barraud, N, Kardak, BG, Yepuri, NR, Howlin, RP, Webb, JS, Faust, SN, Kjelleberg, S, Rice, SA & Kelso, MJ 2012, 'Cephalosporin-3 '-diazeniumdiolates: Targeted NO-Donor Prodrugs for Dispersing Bacterial Biofilms', ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, vol. 51, no. 36, pp. 9057-9060.View/Download from: UTS OPUS or Publisher's site
Chong, G, Kimyon, O, Rice, SA, Kjelleberg, S & Manefield, M 2012, 'The presence and role of bacterial quorum sensing in activated sludge', MICROBIAL BIOTECHNOLOGY, vol. 5, no. 5, pp. 621-633.View/Download from: UTS OPUS or Publisher's site
Ho, KKK, Cole, N, Chen, R, Willcox, MDP, Rice, SA & Kumar, N 2012, 'Immobilization of antibacterial dihydropyrrol-2-ones on functional polymer supports to prevent bacterial infections in vivo.', Antimicrobial Agents and Chemotherapy, vol. 56, no. 2, pp. 1138-1141.View/Download from: UTS OPUS or Publisher's site
Antibiotic-resistant Staphylococcus aureus is of great concern, as it causes a wide range of life-threatening infections. The current study demonstrates that dihydropyrrolone (DHP)-coated polyacrylamide substrates are effective in reducing the number of culturable clinical isolates of S. aureus in vitro in a dose-dependent manner and are able to reduce the pathogenic potential of staphylococcal infection in a subcutaneous infection model. Covalently bound DHPs therefore show great potential for use as an antimicrobial strategy in device-related applications.
Koh, KS, Matz, C, Tan, CH, Le, HL, Rice, SA, Marshall, DJ, Steinberg, PD & Kjelleberg, S 2012, 'Minimal increase in genetic diversity enhances predation resistance', MOLECULAR ECOLOGY, vol. 21, no. 7, pp. 1741-1753.View/Download from: UTS OPUS or Publisher's site
Rice, SA, van den Akker, B, Pomati, F & Roser, D 2012, 'A risk assessment of Pseudomonas aeruginosa in swimming pools: a review', JOURNAL OF WATER AND HEALTH, vol. 10, no. 2, pp. 181-196.View/Download from: UTS OPUS or Publisher's site
Woo, JKK, Webb, JS, Kirov, SM, Kjelleberg, S & Rice, SA 2012, 'Biofilm dispersal cells of a cystic fibrosis Pseudomonas aeruginosa isolate exhibit variability in functional traits likely to contribute to persistent infection', FEMS IMMUNOLOGY AND MEDICAL MICROBIOLOGY, vol. 66, no. 2, pp. 251-264.View/Download from: UTS OPUS or Publisher's site
Steinberg, PD, Rice, SA, Campbell, AH, McDougald, D & Harder, T 2011, 'Interfaces Between Bacterial and Eukaryotic "Neuroecology"', INTEGRATIVE AND COMPARATIVE BIOLOGY, vol. 51, no. 5, pp. 794-806.View/Download from: UTS OPUS or Publisher's site
Ho, KKK, Cole, N, Chen, R, Willcox, MDP, Rice, SA & Kumar, N 2010, 'Characterisation and in vitro activities of surface attached dihydropyrrol-2-ones against Gram-negative and Gram-positive bacteria', BIOFOULING, vol. 26, no. 8, pp. 913-921.View/Download from: Publisher's site
Lauro, FM, McDougald, D, Thomas, T, Williams, TJ, Egan, S, Rice, S, DeMaere, MZ, Ting, L, Ertan, H, Johnson, J, Ferriera, S, Lapidus, A, Anderson, I, Kyrpides, N, Munk, AC, Detter, C, Han, CS, Brown, MV, Robb, FT, Kjelleberg, S & Cavicchioli, R 2009, 'The genomic basis of trophic strategy in marine bacteria', PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, vol. 106, no. 37, pp. 15527-15533.View/Download from: Publisher's site
Rice, SA, Tan, CH, Mikkelsen, PJ, Kung, V, Woo, J, Tay, M, Hauser, A, McDougald, D, Webb, JS & Kjelleberg, S 2009, 'The biofilm life cycle and virulence of Pseudomonas aeruginosa are dependent on a filamentous prophage', ISME JOURNAL, vol. 3, no. 3, pp. 271-282.View/Download from: Publisher's site
Schleheck, D, Barraud, N, Klebensberger, J, Webb, JS, McDougald, D, Rice, SA & Kjelleberg, S 2009, 'Pseudomonas aeruginosa PAO1 Preferentially Grows as Aggregates in Liquid Batch Cultures and Disperses upon Starvation', PLOS ONE, vol. 4, no. 5.View/Download from: UTS OPUS or Publisher's site
Barraud, N, Schleheck, D, Klebensberger, J, Webb, JS, Hassett, DJ, Rice, SA & Kjelleberg, S 2009, 'Nitric Oxide Signaling in Pseudomonas aeruginosa Biofilms Mediates Phosphodiesterase Activity, Decreased Cyclic Di-GMP Levels, and Enhanced Dispersal', JOURNAL OF BACTERIOLOGY, vol. 191, no. 23, pp. 7333-7342.View/Download from: Publisher's site
Barraud, N, Storey, MV, Moore, ZP, Webb, JS, Rice, SA & Kjelleberg, S 2009, 'Nitric oxide-mediated dispersal in single- and multi-species biofilms of clinically and industrially relevant microorganisms', MICROBIAL BIOTECHNOLOGY, vol. 2, no. 3, pp. 370-378.View/Download from: Publisher's site
Willcox, MDP, Zhu, H, Conibear, TCR, Hume, EBH, Givskov, M, Kjelleberg, S & Rice, SA 2008, 'Role of quorum sensing by Pseudomonas aeruginosa in microbial keratitis and cystic fibrosis', MICROBIOLOGY-SGM, vol. 154, pp. 2184-2194.View/Download from: Publisher's site
McDougald, D, Rice, SA & Kjelleberg, S 2007, 'Bacterial quorum sensing and interference by naturally occurring biomimics', ANALYTICAL AND BIOANALYTICAL CHEMISTRY, vol. 387, no. 2, pp. 445-453.View/Download from: Publisher's site
Bacteria communicate with other members of their community through the secretion and perception of small chemical cues or signals. The recognition of a signal normally leads to the expression of a large suite of genes, which in some bacteria are involved in the regulation of virulence factors, and as a result, these signaling compounds are key regulatory factors in many disease processes. Thus, it is of interest when studying pathogens to understand the mechanisms used to control the expression of virulence genes so that strategies might be devised for the control of those pathogens. Clearly, the ability to interfere with this process of signaling represents a novel approach for the treatment of bacterial infections. There is a broad range of compounds that bacteria can use for signaling purposes, including fatty acids, peptides, N-acylated homoserine lactones, and the signals collectively called autoinducer 2 (AI-2). This chapter will focus on the latter two signaling systems as they are present in a range of medically relevant bacteria, and here we describe assays for determining whether an organism produces a particular signal and assays that can be used to identify inhibitors of the signaling cascade. Lastly, the signal detection and inhibition assays will be directly linked to the expression of virulence factors of specific pathogens. © Humana Press.
Kirov, SM, Webb, JS, O'May, CY, Reid, DW, Woo, JKK, Rice, SA & Kjelleberg, S 2007, 'Biofilm differentiation and dispersal in mucoid Pseudomonas aeruginosa isolates from patients with cystic fibrosis', MICROBIOLOGY-SGM, vol. 153, pp. 3264-3274.View/Download from: Publisher's site
Koh, K, Lam, K, Alhede, M, Queck, S, Labbate, M, Kjelleberg, SL & Rice, SA 2007, 'Phenotypic diversification and adaptation of Serratia marcescens MG1 biofilm-derived morphotypes', Journal Of Bacteriology, vol. 189, pp. 119-130.View/Download from: UTS OPUS or Publisher's site
We report here the characterization of dispersal variants from microcolony-type biofilms of Serratia marcescens MG1. Biofilm formation proceeds through a reproducible process of attachment, aggregation, microcolony development, hollow colony formation, and dispersal. From the time when hollow colonies were observed in flow cell biofilms after 3 to 4 days, at least six different morphological colony variants were consistently isolated from the biofilm effluent. The timing and pattern of variant formation were found to follow a predictable sequence, where some variants, such as a smooth variant with a sticky colony texture (SSV), could be consistently isolated at the time when mature hollow colonies were observed, whereas a variant that produced copious amounts of capsular polysaccharide (SUMV) was always isolated at late stages of biofilm development and coincided with cell death and biofilm dispersal or sloughing. The morphological variants differed extensively from the wild type in attachment, biofilm formation, and cell ultrastructure properties. For example, SSV formed two- to threefold more biofilm biomass than the wild type in batch biofilm assays, despite having a similar growth rate and attachment capacity. Interestingly, the SUMV, and no other variants, was readily isolated from an established SSV biofilm, indicating that the SUMV is a second-generation genetic variant derived from SSV. Planktonic cultures showed significantly lower frequencies of variant formation than the biofilms (5.05 x 108 versus 4.83 x 106, respectively), suggesting that there is strong, diversifying selection occurring within biofilms and that biofilm dispersal involves phenotypic radiation with divergent phenotypes.
Labbate, M, Zhu, H, Thung, L, Bandara, R, Learsen, MR, Willcox, MD, Givskov, M, Rice, SA & Kjelleberg, SL 2007, 'Quorum sensing regulation of adhesion in Serratia marcescens is surface dependant', Journal Of Bacteriology, vol. 189, pp. 2702-2711.View/Download from: UTS OPUS or Publisher's site
Serratia marcescens is an opportunistic pathogen and a major cause of ocular infections. In previous studies of S. marcescens MG1, we showed that biofilm maturation and sloughing were regulated by N-acyl homoserine lactone (AHL)-based quorum sensing (QS). Because of the importance of adhesion in initiating biofilm formation and infection, the primary goal of this study was to determine whether QS is important in adhesion to both abiotic and biotic surfaces, as assessed by determining the degree of attachment to hydrophilic tissue culture plates and human corneal epithelial (HCE) cells. Our results demonstrate that while adhesion to the abiotic surface was AHL regulated, adhesion to the HCE cell biotic surface was not. Type I fimbriae were identified as the critical adhesin for non-QS-mediated attachment to the biotic HCE cell surface but played no role in adhesion to the abiotic surface. While we were not able to identify a single QS-regulated adhesin essential for attachment to the abiotic surface, four AHL-regulated genes involved in adhesion to the abiotic surface were identified. Interestingly, two of these genes, bsmA and bsmB, were also shown to be involved in adhesion to the biotic surface in a non-QS-controlled fashion. Therefore, the expression of these two genes appears to be cocontrolled by regulators other than the QS system for mediation of attachment to HCE cells. We also found that QS in S. marcescens regulates other potential cell surface adhesins, including exopolysaccharide and the outer membrane protein OmpX. We concluded that S. marcescens MG1 utilizes different regulatory systems and adhesins in attachment to biotic and abiotic surfaces and that QS is a main regulatory pathway in adhesion to an abiotic surface but not in adhesion to a biotic surface.
McDougald, D, Lin, WH, Rice, SA & Kjelleberg, S 2006, 'The role of quorum sensing and the effect of environmental conditions on biofilm formation by strains of Vibrio vulnificus', BIOFOULING, vol. 22, no. 3, pp. 133-144.View/Download from: Publisher's site
Barraud, N, Hassett, DJ, Hwang, S-H, Rice, SA, Kjelleberg, S & Webb, JS 2006, 'Involvement of nitric oxide in biofilm dispersal of Pseudomonas aeruginosa', JOURNAL OF BACTERIOLOGY, vol. 188, no. 21, pp. 7344-7353.View/Download from: Publisher's site
Queck, S-Y, Weitere, M, Moreno, AM, Rice, SA & Kjelleberg, S 2006, 'The role of quorum sensing mediated developmental traits in the resistance of Serratia marcescens biofilms against protozoan grazing', ENVIRONMENTAL MICROBIOLOGY, vol. 8, no. 6, pp. 1017-1025.View/Download from: Publisher's site
Rice, SA, McDougald, D, Kumar, N & Kjelleberg, S 2005, 'The use of quorum-sensing blockers as therapeutic agents for the control of biofilm-associated infections', Current Opinion in Investigational Drugs, vol. 6, no. 2, pp. 178-184.
The development of novel antimicrobial compounds is required to treat the growing number of infections where antibiotic resistance is a serious threat, especially in situations where biofilms are involved. Antibiotic resistance is the result of two factors: first, through the development of specific antibiotic resistance, due to either mutation or the acquisition of antibiotic resistance genes; and second, by the innate tolerance of bacterial biofilms. Bacterial control, through the inhibition of bacterial cell-cell communication systems which are involved in the regulation of virulence factor production, host colonization, and biofilm formation, is discussed in this review. Specifically, this review presents current studies on the development of quorum-sensing inhibitors for the control of bacterial infections. © The Thomson Corporation.
Fagerlind, MG, Nilsson, P, Harlen, M, Karlsson, S, Rice, SA & Kjelleberg, S 2005, 'Modeling the effect of acylated homoserine lactone antagonists in Pseudomonas aeruginosa', BIOSYSTEMS, vol. 80, no. 2, pp. 201-213.View/Download from: Publisher's site
Gob, WK, Rice, SA & Kumar, N 2005, 'Theoretical study of molecular determinants involved in signal binding to the TraR protein of Agrobacterium tumefaciens', MOLECULES, vol. 10, no. 10, pp. 1263-1271.View/Download from: Publisher's site
Weitere, M, Bergfeld, T, Rice, SA, Matz, C & Kjelleberg, S 2005, 'Grazing resistance of Pseudomonas aeruginosa biofilms depends on type of protective mechanism, developmental stage and protozoan feeding mode', ENVIRONMENTAL MICROBIOLOGY, vol. 7, no. 10, pp. 1593-1601.View/Download from: Publisher's site
Rice, SA, Koh, K, Queck, S, Labbate, M, Lam, K & Kjelleberg, SL 2005, 'Biofilm formation and sloughing in Serratia marcescens is controlled by quorum sensing and nutrient conditions', Journal Of Bacteriology, vol. 187, no. 10, pp. 3477-3485.View/Download from: UTS OPUS or Publisher's site
We describe here a role for quorum sensing in the detachment, or sloughing, of Serratia marcescens filamentous biofilms, and we show that nutrient conditions affect the biofilm morphotype. Under reduced carbon or nitrogen conditions, S. marcescens formed a classical biofilm consisting of microcolonies. The filamentous biofilm could be converted to a microcolony-type biofilm by switching the medium after establishment of the biofilm. Similarly, when initially grown as a microcolony biofilm, S. marcescens could be converted back to a filamentous biofilm by increasing the nutrient composition. Under high-nutrient conditions, an N-acyl homoserine lactone quorum-sensing mutant formed biofilms that were indistinguishable from the wild-type biofilms. Similarly, other quorum-sensing-dependent behaviors, such as swarming motility, could be rendered quorum sensing independent by manipulating the growth medium. Quorum sensing was also found to be involved in the sloughing of the filamentous biofilm. The biofilm formed by the bacterium consistently sloughed from the substratum after approximately 75 to 80 h of development.
Matz, C, Bergfeld, T, Rice, SA & Kjelleberg, S 2004, 'Microcolonies, quorum sensing and cytotoxicity determine the survival of Pseudomonas aeruginosa biofilms exposed to protozoan grazing', ENVIRONMENTAL MICROBIOLOGY, vol. 6, no. 3, pp. 218-226.View/Download from: Publisher's site
Zhu, H, Bandara, R, Conibear, TCR, Thuruthyil, SJ, Rice, SA, Kjelleberg, S, Givskov, M & Willcox, MDP 2004, 'Pseudomonas aeruginosa with LasI quorum-sensing deficiency during corneal infection', INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE, vol. 45, no. 6, pp. 1897-1903.View/Download from: Publisher's site
Labbate, M, Queck, S, Koh, K, Rice, SA, Givskov, M & Kjelleberg, SL 2004, 'Quorum sensing-controlled biofilm development in Serratia liquefaciens MG1', Journal Of Bacteriology, vol. 186, pp. 692-698.View/Download from: UTS OPUS or Publisher's site
Serratia liquefaciens MG1 contains an N-acylhomoserine lactone-mediated quorum-sensing system that is known to regulate swarming motility colonization. In this study, we describe for S. liquefaciens MG1 the development of a novel biofilm consisting of cell aggregates and differentiated cell types, such as cell chains and long filamentous cells. Furthermore, quorum sensing is shown to be crucial for normal biofilm development and for elaborate differentiation. A mutant of S. liquefaciens MG1 that was incapable of synthesizing extracellular signal formed a thin and nonmature biofilm lacking cell aggregates and differentiated cell chains. Signal-based complementation of this mutant resulted in a biofilm with the wild-type architecture. Two quorum-sensing-regulated genes (bsmA and bsmB) involved in biofilm development were identified, and we propose that these genes are engaged in fine-tuning the formation of cell aggregates at a specific point in biofilm development.
McDougald, D, Srinivasan, S, Rice, SA & Kjelleberg, S 2003, 'Signal-mediated cross-talk regulates stress adaptation in Vibrio species', MICROBIOLOGY-SGM, vol. 149, pp. 1923-1933.View/Download from: Publisher's site
McDougald, D, Srinivasan, S, Rice, SA & Kjelleberg, S 2003, 'Signal-mediated cross-talk regulates stress adaptation in Vibrio species', Microbiology, vol. 149, no. 7, pp. 1923-1933.View/Download from: Publisher's site
Quorum sensing systems serve as a means of 'census taking' of conspecific and non-conspecific bacteria in the near vicinity. The acylated homoserine lactone (AHL) quorum sensing system has been proposed to be primarily an intra-specific communication system, while the AI-2 autoinducer signalling system is proposed to be an interspecific communication system. Here it is shown that AI-2-like signalling in two marine Vibrio species, Vibrio vulnificus and 'Vibrio angustum' S14, induces the core response phenotypes of starvation adaptation and stress resistance, and that a signal antagonist can competitively inhibit these phenotypes. Furthermore, the signals produced by a range of Vibrio species have the ability to induce these phenotypes in V. vulnificus and 'V. angustum' S14, indicating that, at least in Vibrio species, AI-2-like signalling systems function as interspecies communication systems capable of 'cross-talk' and of regulating environmentally relevant phenotypes.
Fagerlind, MG, Rice, SA, Nilsson, P, Harlen, M, James, S, Charlton, T & Kjelleberg, S 2003, 'The role of regulators in the expression of quorum-sensing signals in Pseudomonas aeruginosa', JOURNAL OF MOLECULAR MICROBIOLOGY AND BIOTECHNOLOGY, vol. 6, no. 2, pp. 88-100.View/Download from: Publisher's site
Ritchie, AJ, Yam, AOW, Tanabe, KM, Rice, SA & Cooley, MA 2003, 'Modification of in vivo and in vitro T- and B-cell-mediated immune responses by the Pseudomonas aeruginosa quorum-sensing molecule n-(3-oxododecanoyl)-L-homoserine lactone', Infection and Immunity, vol. 71, no. 8, pp. 4421-4431.View/Download from: Publisher's site
N-3-(oxododecanoyl)-L-homoserine lactone (OdDHL), a quorum-sensing molecule of Pseudomonas aeruginosa, plays an important role in the pathogenesis of the organism through its control of virulence factor expression. Several reports have suggested that OdDHL can also directly modulate host immune responses. However, the nature of the modulation is controversial, with different reports suggesting promotion of either humoral (Th2-mediated) or inflammatory (Th1-mediated) responses. This report describes a series of studies which demonstrate for the first time that in vivo administration of OdDHL can modulate the course of an antibody response, with an increase in ovalbumin (OVA)-specific immunogloblulin G1 (IgG1) but not IgG2a in OdDHL-treated OVA-immunized BALB/c mice compared to levels for controls. In vitro stimulation of lymphocytes from both Th1-biased C57B1/6 and T-cell receptor transgenic mice and Th2-biased BALB/c mice in the presence of OdDHL demonstrated that OdDHL inhibits in vitro cytokine production in response to both mitogen and antigen, with gamma interferon (IFN-γ) tending to be more inhibited than interleukin-4 (IL-4). In vitro mitogen or antigen restimulation of cells from mice treated with OdDHL in vivo shows effects on cytokine production which depend on the underlying immune bias of the mouse strain used, with a relative increase of IFN-γ in Th1-biased C57B1/6 mice and a relative increase of IL-4 in Th2-biased BALB/c mice. Thus, the mode of action of OdDHL on T-cell cytokine production is likely to be a relatively nonspecific one which accentuates an underlying immune response bias rather than one which specifically targets either Th1 or Th2 responses.
Ritchie, AJ, Yam, AOW, Tanabe, KM, Rice, SA & Cooley, MA 2003, 'Modification of in vivo and in vitro T- and B-cell-mediated immune responses by the Pseudomonas aeruginosa quorum-sensing molecule N-(3-oxododecanoyl)-L-homoserine lactone', INFECTION AND IMMUNITY, vol. 71, no. 8, pp. 4421-4431.View/Download from: Publisher's site
Thompson, LS, Webb, JS, Rice, SA & Kjelleberg, S 2003, 'The alternative sigma factor RpoN regulates the quorum sensing gene rhlI in Pseudomonas aeruginosa', FEMS MICROBIOLOGY LETTERS, vol. 220, no. 2, pp. 187-195.View/Download from: Publisher's site
McDougald, D, Gong, L, Srinivasan, S, Hild, E, Thompson, L, Takayama, K, Rice, SA & Kjelleberg, S 2002, 'Defences against oxidative stress during starvation in bacteria', ANTONIE VAN LEEUWENHOEK INTERNATIONAL JOURNAL OF GENERAL AND MOLECULAR MICROBIOLOGY, vol. 81, no. 1-4, pp. 3-13.View/Download from: Publisher's site
Hentzer, M, Riedel, K, Rasmussen, TB, Heydorn, A, Andersen, JB, Parsek, MR, Rice, SA, Eberl, L, Molin, S, Hoiby, N, Kjelleberg, S & Givskov, M 2002, 'Inhibition of quorum sensing in Pseudomonas aeruginosa biofilm bacteria by a halogenated furanone compound', MICROBIOLOGY-SGM, vol. 148, pp. 87-102.View/Download from: Publisher's site
Lampson, BC, Xu, CY, Rice, SA & Inouye, S 2002, 'A partial copy of msDNA from a new retron element is likely a retrotransposed DNA found in the myxobacterium Nannocystis exedens', GENE, vol. 299, no. 1-2, pp. 251-261.View/Download from: Publisher's site
McDougald, D, Rice, SA & Kjelleberg, S 2001, 'SmcR-dependent regulation of adaptive phenotypes in Vibrio vulnificus', JOURNAL OF BACTERIOLOGY, vol. 183, no. 2, pp. 758-762.View/Download from: Publisher's site
Nilsson, P, Olofsson, A, Fagerlind, M, Fagerstrom, T, Rice, S, Kjelleberg, S & Steinberg, P 2001, 'Kinetics of the AHL regulatory system in a model biofilm system: How many bacteria constitute a "quorum"?', JOURNAL OF MOLECULAR BIOLOGY, vol. 309, no. 3, pp. 631-640.View/Download from: Publisher's site
McDougald, D, Rice, SA & Kjellberg, S 2000, 'The marine pathogen Vibrio vulnificus encodes a putative homologue of the Vibrio harveyi regulatory gene, luxR: a genetic and phylogenetic comparison', GENE, vol. 248, no. 1-2, pp. 213-221.View/Download from: Publisher's site
Rice, SA, McDougald, D & Kjelleberg, S 2000, 'Vibrio vulnificus: A physiological and genetic approach to the viable but nonculturable response', Journal of Infection and Chemotherapy, vol. 6, no. 2, pp. 115-120.View/Download from: Publisher's site
In this review, we focus on studies of the viable but nonculturable response (VBNC) of Vibrio vulnificus, a significant and aggressive human pathogen, as a model system for the general understanding of the VBNC response. This response is characterized physiologically as the inability to culture an organism on media that normally supports its growth, and yet those cells retain indicators of metabolic activity. Implicit in this definition is that it may be possible to return or resuscitate VBNC cells to active division on laboratory media. Since its original description in 1985, the VBNC response has been recognized in a range of bacteria. Study of the VBNC response has traditionally focused on physiological methods aimed at demonstrating that VBNC cells are indeed viable but have a specific block that prevents them from dividing on laboratory media, and such study has attempted to identify conditions that unequivocally demonstrate the resuscitation of VBNC cells. With the advent of molecular genetics, VBNC studies have begun to focus on genetics as a means to determine whether there are specific genes or regulatory pathways responsible for the development of the VBNC response. Thus, by combining information from physiological and genetic experiments, it is hoped that it can be determined whether the VBNC response represents a genetically programmed physiological adaptation similar to sporulation and outgrowth or whether VBNC represents the slow loss of function on the way to cellular death.
Manefield, M, Harris, L, Rice, SA, De Nys, R & Kjelleberg, S 2000, 'Inhibition of luminescence and virulence in the black tiger prawn (Penaeus monodon) pathogen Vibrio harveyi by intercellular signal antagonists', APPLIED AND ENVIRONMENTAL MICROBIOLOGY, vol. 66, no. 5, pp. 2079-2084.View/Download from: Publisher's site
Holden, MTG, Chhabra, SR, de Nys, R, Stead, P, Bainton, NJ, Hill, PJ, Manefield, M, Kumar, N, Labatte, M, England, D, Rice, S, Givskov, M, Salmond, GPC, Stewart, GSAB, Bycroft, BW, Kjelleberg, SA & Williams, P 1999, 'Quorum-sensing cross talk: isolation and chemical characterization of cyclic dipeptides from Pseudomonas aeruginosa and other Gram-negative bacteria', MOLECULAR MICROBIOLOGY, vol. 33, no. 6, pp. 1254-1266.View/Download from: Publisher's site
Lampson, BC & Rice, SA 1997, 'Repetitive sequences found in the chromosome of the myxobacterium Nannocystis exedens are similar to msDNA: A possible retrotransposition event in bacteria', MOLECULAR MICROBIOLOGY, vol. 23, no. 4, pp. 813-823.View/Download from: Publisher's site
Rice, S & Pamphlett, R 1997, 'Study linking enteroviral infection with motor neurone disease is not confirmed', BRITISH MEDICAL JOURNAL, vol. 315, no. 7119, pp. 1380-1380.View/Download from: Publisher's site
RICE, SA & LAMPSON, BC 1995, 'PHYLOGENETIC COMPARISON OF RETRON ELEMENTS AMONG THE MYXOBACTERIA - EVIDENCE FOR VERTICAL INHERITANCE', JOURNAL OF BACTERIOLOGY, vol. 177, no. 1, pp. 37-45.View/Download from: Publisher's site
RICE, SA, BIEBER, J, CHUN, JY, STACEY, G & LAMPSON, BC 1993, 'DIVERSITY OF RETRON ELEMENTS IN A POPULATION OF RHIZOBIA AND OTHER GRAM-NEGATIVE BACTERIA', JOURNAL OF BACTERIOLOGY, vol. 175, no. 13, pp. 4250-4254.View/Download from: Publisher's site
Leong, W, Lutz, C, Williams, J, Poh, YH, Yeo, BKY, Chua, C, Rice, SA, Givskov, M, Sanderson-Smith, M & McDougald, D, 'Pseudomonas aeruginosa isolates co-incubated with Acanthamoeba castellanii exhibit phenotypes similar to chronic cystic fibrosis isolates'.View/Download from: Publisher's site
The opportunistic pathogen, Pseudomonas aeruginosa, is ubiquitous in the environment, and in humans is capable of causing acute and chronic infections. P. aeruginosa, when co-incubated with the bacterivorous amoeba, Acanthamoeba castellanii, for extended periods, produced genetic and phenotypic variants. Sequencing of late-stage amoeba-adapted P. aeruginosa isolates demonstrated single nucleotide polymorphisms within genes that encode known virulence factors, and this correlated with a reduction in expression of virulence traits. Virulence towards the nematode, Caenorhabditis elegans, was attenuated in late-stage amoeba-adapted P. aeruginosa compared to early stage amoeba-adapted and non-adapted counterparts. Late-stage amoeba-adapted P. aeruginosa lost competitive fitness compared to non-adapted counterparts when grown in nutrient rich media. However, non-adapted P. aeruginosa were rapidly cleared by amoeba predation, whereas late-stage amoeba-adapted isolates remained in higher numbers 24 h after ingestion by amoeba. In addition, there was reduced uptake by macrophage of amoeba-adapted isolates and reduced uptake by human neutrophils as well as increased survival in the presence of neutrophils. Our findings indicate that the selection imposed by amoeba on P. aeruginosa resulted in reduced virulence over time. Importantly, the genetic and phenotypic traits possessed by late-stage amoeba-adapted P. aeruginosa are similar to what is observed for isolates obtained from chronic cystic fibrosis infections. This notable overlap in adaptation to different host types suggests similar selection pressures among host cell types.
Karampatzakis, A, Sankaran, J, Kandaswamy, K, Rice, SA, Cohen, Y & Wohland, T, 'Measurement of oxygen concentrations in bacterial biofilms using transient state monitoring by single plane illumination microscopy', Biomedical Physics & Engineering Express, vol. 3, no. 3, pp. 035020-035020.View/Download from: UTS OPUS or Publisher's site
Harder, T, Rice, SA, Dobretsov, S, Thomas, T, Carre-Mlouka, A, Kjelleberg, S, Steinberg, P & McDougald, D 2014, 'Bacterial communication systems' in La Barre, S & Komprobst, JM (eds), Outstanding Marine Molecules, Wiley-Blackwell, USA, pp. 173-187.View/Download from: UTS OPUS or Publisher's site
Like multicellular organisms, bacteria can regulate gene expression at the multicellular level. The coordination of multicellular bacterial behavior occurs via a chemically mediated process known as quorum sensing (QS). Currently, there are five well-defined classes of chemical signals in bacteria that support the concept of QS. By coupling an extracellular bacterial signal with gene expression, bacteria can control gene expression in such a way that the majority of the population expresses the same phenotype simultaneously. In this chapter, the molecular mechanisms of QS, the effective range of QS-regulated processes, and the ecological role of quorum quenching, namely the inhibition of QS, are discussed. QS occurs most frequently in bacterial species that associate with surfaces or higher organisms, either as a pathogen or as a beneficial associate. Three seminal examples of QS-mediated cross-kingdom signaling in the marine environment are reviewed: (i) the chemical defense of the red seaweed Delisea pulchra; (ii) the mutualistic association of Vibrio fischeri with the Hawaiian bobtail squid; and (iii) the exploitation of bacterial QS during settlement of marine spores and invertebrate larvae.
Mcdougald, D, Klebensberger, J, Tolker-Nielsen, T, Webb, JS, Conibear, T, Rice, SA, Kirov, SM, Matz, C & Kjelleberg, S 2008, 'Pseudomonas aeruginosa: A Model for Biofilm Formation' in Pseudomonas: Model Organism, Pathogen, Cell Factory, pp. 215-253.View/Download from: Publisher's site
Rice, SA & Kjelleberg, S 2006, 'Bacterial biofilm formation, adaptation and fitness' in Microbial Ecology of Aerial Plant Surfaces, pp. 67-82.
Zhu, H, Thuruthyil, SJ, Rice, S, Kjelleberg, S, Kumar, N, Read, RW, Erickson, P & Willcox, MDP 2002, 'Inhibition of Pseudomonas aeruginosa virulence factors by furanones', INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE, Annual Meeting of the Association-for-Research-in-Vision-and-Ophthalmology, ASSOC RESEARCH VISION OPHTHALMOLOGY INC, FT LAUDERDALE, FLORIDA, pp. U207-U207.
Rice, SA, Givskov, M, Steinberg, P & Kjelleberg, S 1999, 'Bacterial signals and antagonists: The interaction between bacteria and higher organisms', Journal of Molecular Microbiology and Biotechnology, pp. 23-31.
It is now well established that bacteria communicate through the secretion and uptake of small diffusable molecules. These chemical cues, or signals, are often used by bacteria to coordinate phenotypic expression and this mechanism of regulation presumably provides them with a competitive advantage in their natural environment. Examples of coordinated behaviors of marine bacteria which are regulated by signals include swarming and exoprotease production, which are important for niche colonisation or nutrient acquisition (e.g. protease breakdown of substrate). While the current focus on bacterial signalling centers on N-Acylated homoserine lactones, the quorum sensing signals of Gram-negative bacteria, these are not the only types of signals used by bacteria. Indeed, there appears to be many other types of signals produced by bacteria and it also appears that a bacterium may use multiple classes of signals for phenotypic regulation. Recent work in the area of marine microbial ecology has led to the observation that some marine eukaryotes secrete their own signals which compete with the bacterial signals and thus inhibit the expression of bacterial signalling phenotypes. This type of molecular mimicry has been well characterised for the interaction of marine prokaryotes with the red alga, Delisea pulchra.