Associate Professor Diane McDougald leads the Pathogen Evolution group located at The ithree Institute (Infection, Immunology and Innovation), University of Technology Sydney. She is also a Visiting Senior Researcher at the Singapore Centre on Environmental Life Sciences Engineering at Nanyang Technological University, Singapore. A/Prof McDougald has made significant contributions to the fields of Vibrio biology, bacterial adaptation to stress and mechanisms of molecular control of these responses, cell-to-cell communication, biofilm formation and interactions of bacteria with higher eukaryotes.
Diane McDougald has over 20 years experience investigating mechanisms of survival and persistence of pathogens in the environment. She has made significant contributions to the fields of Vibriobiology, bacterial adaptation to stress and mechanisms of molecular control of these responses, cell-to-cell communication, biofilm formation and interactions of bacteria with higher eukaryotes. Outcomes of her research were instrumental in establishing Biosignal Ltd, a biotechnology company whose patents have since been acquired by Unilever for development of anti-biofilm compounds to reduce bacteria's ability to form biofilms on surfaces such as medical devices, gas pipelines, and lungs. PhD students she has supervised have gone on to positions in academia and in the water/wastewater industry.
Can supervise: YES
The Pathogen Evolution group’s major research interests are the mechanisms of survival and persistence of pathogens in the environment, and what impact these mechanisms have on virulence and pathogenicity in the host. The team investigates the evolutionary drivers and consequences of bacterial adaptation to stresses, including interactions with higher organisms. Broadly, the team studies the interactions of prokaryotes and eukaryotes using a number of model systems to investigate the impact of predation by protozoa on microbial communities and how evolution of grazing defences drives the evolution of pathogenicity in the environment. Predation is an important selection pressure that pathogens face in the environment, and as a result, pathogens may evolve phenotypes that not only increase their fitness in the environment, but may also increase their fitness in the human host. This research platform will allow us to test key aspects of the Coincidental Selection Hypothesis, which states that the virulence of many opportunistic human pathogens may be an accidental by-product of selection for adaptations not related to human disease. Predicting the emergence of new pathogens is difficult but important for developing public policy. Building predictive tools relies on high quality knowledge input to which knowledge of the evolutionary drivers and consequences of bacterial adaptation to stresses can make important contributions.
Espinoza-Vergara, G, Noorian, P, Silva-Valenzuela, CA, Raymond, BBA, Allen, C, Hoque, MM, Sun, S, Johnson, MS, Pernice, M, Kjelleberg, S, Djordjevic, SP, Labbate, M, Camilli, A & McDougald, D 2019, 'Vibrio cholerae residing in food vacuoles expelled by protozoa are more infectious in vivo', Nature Microbiology.View/Download from: UTS OPUS or Publisher's site
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.
Vibrio vulnificus, a ubiquitous inhabitant of coastal marine environments, has been isolated from a variety of sources. It is an opportunistic pathogen of both marine animals and humans. Here, the genome sequence of V. vulnificus Env1, an environmental isolate resistant to predation by the ciliate Tetrahymena pyriformis, is reported.
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.
Sun, S, Noorian, P & McDougald, D 2018, 'Dual Role of Mechanisms Involved in Resistance to Predation by Protozoa and Virulence to Humans.', Frontiers in microbiology, vol. 9.View/Download from: UTS OPUS or Publisher's site
Most opportunistic pathogens transit in the environment between hosts and the environment plays a significant role in the evolution of protective traits. The coincidental evolution hypothesis suggests that virulence factors arose as a response to other selective pressures rather for virulence per se. This idea is strongly supported by the elucidation of bacterial-protozoal interactions. In response to protozoan predation, bacteria have evolved various defensive mechanisms which may also function as virulence factors. In this review, we summarize the dual role of factors involved in both grazing resistance and human pathogenesis, and compare the traits using model intracellular and extracellular pathogens. Intracellular pathogens rely on active invasion, blocking of the phagosome and lysosome fusion and resistance to phagocytic digestion to successfully invade host cells. In contrast, extracellular pathogens utilize toxin secretion and biofilm formation to avoid internalization by phagocytes. The complexity and diversity of bacterial virulence factors whose evolution is driven by protozoan predation, highlights the importance of protozoa in evolution of opportunistic pathogens.
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
Noorian, P, Hu, J, Chen, Z, Kjelleberg, S, Wilkins, MR, Sun, S & McDougald, D 2017, 'Pyomelanin produced by Vibrio cholerae confers resistance to predation by Acanthamoeba castellanii.', FEMS Microbiology Ecology, vol. 93, no. 12, pp. 1-10.View/Download from: UTS OPUS or Publisher's site
Protozoan predation is one of the main environmental factors constraining bacterial growth in aquatic environments, and thus has led to the evolution of a number of defence mechanisms that protect bacteria from predation. These mechanisms may also function as virulence factors in infection of animal and human hosts. Whole transcriptome shotgun sequencing of Vibrio cholerae biofilms during predation by the amoebae, Acanthamoeba castellanii, revealed that 131 transcripts were significantly differentially regulated when compared to the non-grazed control. Differentially regulated transcripts included those involved in biosynthetic and metabolic pathways. The transcripts of genes involved in tyrosine metabolism were down-regulated in the grazed population, which indicates that the tyrosine metabolic regulon may have a role in the response of V. cholerae biofilms to A. castellanii predation. Homogentisate 1, 2-dioxygenase (HGA) is the main intermediate of the normal L-tyrosine catabolic pathway which is known to auto-oxidize, leading to the formation of the pigment, pyomelanin. Indeed, a pigmented mutant, disrupted in hmgA, was more resistant to amoebae predation than the wild type. Increased grazing resistance was correlated with increased production of pyomelanin and thus reactive oxygen species (ROS), suggesting that ROS production is a defensive mechanism used by bacterial biofilms against predation by amoebae A. castellanii.
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
Chavez-Dozal, AA, Nourabadi, N, Erken, M, McDougald, D & Nishiguchi, MK 2016, 'Comparative analysis of quantitative methodologies for Vibrionaceae biofilms', FOLIA MICROBIOLOGICA, vol. 61, no. 6, pp. 449-453.View/Download from: UTS OPUS or Publisher's site
Guest, JR, Low, J, Tun, K, Wilson, B, Ng, C, Raingeard, D, Ulstrup, KE, Tanzil, JTI, Todd, PA, Toh, TC, McDougald, D, Chou, LM & Steinberg, PD 2016, 'Coral community response to bleaching on a highly disturbed reef', SCIENTIFIC REPORTS, vol. 6.View/Download from: UTS OPUS or Publisher's site
Levin, RA, Beltran, VH, Hill, R, Kjelleberg, S, McDougald, D, Steinberg, PD & van Oppen, MJH 2016, 'Sex, Scavengers, and Chaperones: Transcriptome Secrets of Divergent Symbiodinium Thermal Tolerances', MOLECULAR BIOLOGY AND EVOLUTION, vol. 33, no. 9, pp. 2201-2215.View/Download from: UTS OPUS or Publisher's site
© 2015 Lutz et al. Shewanella sp. CP20 is a marine bacterium that survives ingestion by Tetrahymena pyriformis and is expelled from the protozoan within membrane-bound vacuoles, where the bacterial cells show long-term survival. Here, we report the draft genome sequence of Shewanella sp. CP20 and discuss the potential mechanisms facilitating intraprotozoan survival.
Akhondi, E, Wu, B, Sun, S, Marxer, B, Lim, W, Gu, J, Liu, L, Burkhardt, M, McDougald, D, Pronk, W & Fane, AG 2015, 'Gravity-driven membrane filtration as pretreatment for seawater reverse osmosis: Linking biofouling layer morphology with flux stabilization', WATER RESEARCH, vol. 70, pp. 158-173.View/Download from: UTS OPUS or Publisher's site
Members of the genus Vibrio are known to interact with phyto- and zooplankton in aquatic environments. These interactions have been proven to protect the bacterium from various environmental stresses, serve as a nutrient source, facilitate exchange of DNA, and to serve as vectors of disease transmission. This review highlights the impact of Vibrio-zooplankton interactions at the ecosystem scale and the importance of studies focusing on a wide range of Vibrio-zooplankton interactions. The current knowledge on chitin utilization (i.e., chemotaxis, attachment, and degradation) and the role of these factors in attachment to nonchitinous zooplankton is also presented.
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
Sodhi, N, Rice, SA, Kjelleberg, S & McDougald, D 2015, 'Assessment of the role of extracellular DNA and protozoan grazing in aerobic granular sludge development.', Jacobs Journal of Biotechnology and Bioengineering, vol. 1, no. 2, pp. 1-8.
A scaled-down batch reactor system, modelled on traditional laboratory scale batch reactors, was developed for the preliminary assessment of the role of a number of factors on microbial aggregation. Long-term batch reactors were used to investigate the role of extracellular DNA in the re-granulation of crushed granular sludge, while short-term reactors were used to assess the impact of protozoan grazing on aggregation and microbial community structure. Extracellular DNA was observed as halos and honeycomb structures within granules and was found to be integral to granular architecture. Grazing by heterotrophic protists was shown to increase and maintain aggregate size as well as significantly affect the microbial community structure.
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
Lauro, FM, Senstius, SJ, Cullen, J, Neches, R, Jensen, RM, Brown, MV, Darling, AE, Givskov, M, McDougald, D, Hoeke, R, Ostrowski, M, Philip, GK, Paulsen, IT & Grzymski, JJ 2014, 'The common oceanographer: crowdsourcing the collection of oceanographic data.', PLoS biology, vol. 12, no. 9, pp. e1001947-e1001947.View/Download from: UTS OPUS or 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.
Ling, GC, Low, MH, Erken, M, Longford, S, Nielsen, S, Poole, AJ, Steinberg, P, McDougald, D & Kjelleberg, S 2014, 'Micro-fabricated polydimethyl siloxane (PDMS) surfaces regulate the development of marine microbial biofilm communities.', Biofouling, vol. 30, no. 3, pp. 323-335.View/Download from: UTS OPUS or Publisher's site
This study explored an antifouling (AF) concept based on deployment of microfabricated polydimethyl siloxane (PDMS) surfaces with 1-10 μm periodicity corrugated topographies in temperate marine waters. The effect of the surfaces on the development of microbial biofilms over 28 days and during different seasons, including both summer and winter, was examined using confocal laser scanning microscopy (CLSM) as well as terminal restriction fragment (T-RF) analysis for phylogenetic fingerprinting. The microscale topography significantly impacted biofilm development by altering the attachment pattern and reducing microcolony formation on the 1, 2 and 4 μm PDMS surfaces. Also, field deployments over 28 days showed a significant reduction in biovolume on the 4 and 10 μm PDMS surfaces despite altered environmental conditions. The microfabricated PDMS surfaces further significantly impacted on the community composition of the biofilms, as revealed by changes in T-RF profiles, at different stages of development. Moreover, altered biofilm resistance was demonstrated by exposing pre-established biofilms on 10 μm micro-fabricated surfaces to enhanced flagellate predation by a heterotrophic protist, Rhynchomonas nasuta. Pronounced changes in the overall marine microbial biofilm development as well as community composition warrant exploring substratum modification for marine AF applications.
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.
Mazel, D, Colwell, R, Klose, K, Oliver, J, Crumlish, M, McDougald, D, Bland, MJ & Austin, B 2014, 'VIBRIO 2014 meeting report', RESEARCH IN MICROBIOLOGY, vol. 165, no. 10, pp. 857-864.View/Download from: Publisher's site
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, 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
Chavez-Dozal, A, Gorman, C, Erken, M, Steinberg, PD, McDougald, D & Nishiguchi, MK 2013, 'Predation Response of Vibrio fischeri Biofilms to Bacterivorus Protists', APPLIED AND ENVIRONMENTAL MICROBIOLOGY, vol. 79, no. 2, pp. 553-558.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
Erken, M, Lutz, C & McDougald, D 2013, 'The Rise of Pathogens: Predation as a Factor Driving the Evolution of Human Pathogens in the Environment', MICROBIAL ECOLOGY, vol. 65, no. 4, pp. 860-868.View/Download from: UTS OPUS or Publisher's site
Goh, S, Zhang, Q, Zhang, J, McDougald, D, Krantz, WB, Liu, Y & Fane, AG 2013, 'Impact of a biofouling layer on the vapor pressure driving force and performance of a membrane distillation process', JOURNAL OF MEMBRANE SCIENCE, vol. 438, pp. 140-152.View/Download from: UTS OPUS or Publisher's site
Lutz, C, Erken, M, Noorian, P, Sun, S & McDougald, D 2013, 'Environmental reservoirs and mechanisms of persistence of Vibrio cholerae', FRONTIERS IN MICROBIOLOGY, vol. 4.View/Download from: UTS OPUS or Publisher's site
Sun, S, Kjelleberg, S & McDougald, D 2013, 'Relative Contributions of Vibrio Polysaccharide and Quorum Sensing to the Resistance of Vibrio cholerae to Predation by Heterotrophic Protists', PLOS ONE, vol. 8, no. 2.View/Download from: UTS OPUS or Publisher's site
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
Lay, WCL, Zhang, Q, Zhang, J, McDougald, D, Tang, C, Wang, R, Liu, Y & Fane, AG 2012, 'Effect of Pharmaceuticals on the Performance of a Novel Osmotic Membrane Bioreactor (OMBR)', SEPARATION SCIENCE AND TECHNOLOGY, vol. 47, no. 4, pp. 543-554.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
Anderson, R, Kjelleberg, S, McDougald, D & Juergens, K 2011, 'Species-specific patterns in the vulnerability of carbon-starved bacteria to protist grazing', AQUATIC MICROBIAL ECOLOGY, vol. 64, no. 2, pp. 105-116.View/Download from: UTS OPUS or Publisher's site
Erken, M, Weitere, M, Kjelleberg, S & McDougald, D 2011, 'In situ grazing resistance of Vibrio cholerae in the marine environment', FEMS MICROBIOLOGY ECOLOGY, vol. 76, no. 3, pp. 504-512.View/Download from: UTS OPUS or Publisher's site
Lay, WCL, Zhang, Q, Zhang, J, McDougald, D, Tang, C, Wang, R, Liu, Y & Fane, AG 2011, 'Study of integration of forward osmosis and biological process: Membrane performance under elevated salt environment', DESALINATION, vol. 283, pp. 123-130.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
Steinberg, PD, Marshall, D, McDougald, D & Kjelleberg, S 2010, 'Bacteria are more like corals than bees', Science, vol. e-letter, no. August 25, pp. 658-667.
Thompson, FL, Thompson, CC, Vicente, ACP & Klose, KE 2010, 'Vibrio2009: the third international conference on the biology of Vibrios', MOLECULAR MICROBIOLOGY, vol. 77, no. 5, pp. 1065-1071.View/Download from: Publisher's site
Thompson, FL, Thompson, CC, Vicente, ACP, Klose, KE & the AVib Group 2010, 'Vibrio2009: the third international conference on the biology of Vibrios', Molecular Microbiology, vol. 5, no. 77, pp. 1065-1071.
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
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
Mueller, RS, McDougald, D, Cusumano, D, Sodhi, N, Kjelleberg, S, Azam, F & Bartlett, DH 2007, 'Vibrio cholerae strains possess multiple strategies for abiotic and biotic surface colonization', JOURNAL OF BACTERIOLOGY, vol. 189, no. 14, pp. 5348-5360.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.
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
Matz, C, McDougald, D, Moreno, AM, Yung, PY, Yildiz, FH & Kjelleberg, S 2005, 'Biofilm formation and phenotypic variation enhance predation-driven persistence of Vibrio cholerae', PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, vol. 102, no. 46, pp. 16819-16824.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.
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.
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
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
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.
Weichart, D, McDougald, D, Jacobs, D & Kjelleberg, S 1997, 'In situ analysis of nucleic acids in cold-induced nonculturable Vibrio vulnificus', APPLIED AND ENVIRONMENTAL MICROBIOLOGY, vol. 63, no. 7, pp. 2754-2758.
PaludanMuller, C, Weichart, D, McDougald, D & Kjelleberg, S 1996, 'Analysis of starvation conditions that allow for prolonged culturability of Vibrio vulnificus at low temperature', MICROBIOLOGY-UK, vol. 142, pp. 1675-1684.View/Download from: Publisher's site
OLIVER, JD, HITE, F, MCDOUGALD, D, ANDON, NL & SIMPSON, LM 1995, 'ENTRY INTO, AND RESUSCITATION FROM, THE VIABLE BUT NONCULTURABLE STATE BY VIBRIO-VULNIFICUS IN AN ESTUARINE ENVIRONMENT', APPLIED AND ENVIRONMENTAL MICROBIOLOGY, vol. 61, no. 7, pp. 2624-2630.
OLIVER, JD, MCDOUGALD, D, BARRETT, T, GLOVER, LA & PROSSER, JI 1995, 'EFFECT OF TEMPERATURE AND PLASMID CARRIAGE ON NONCULTURABILITY IN ORGANISMS TARGETED FOR RELEASE', FEMS MICROBIOLOGY ECOLOGY, vol. 17, no. 4, pp. 229-237.
MCDOUGALD, D, SIMPSON, LM, OLIVER, JD & HUDSON, MC 1994, 'TRANSFORMATION OF VIBRIO-VULNIFICUS BY ELECTROPORATION', CURRENT MICROBIOLOGY, vol. 28, no. 5, pp. 289-291.View/Download from: Publisher's site
Morris, JGJ, Wright, AC, Roberts, DM, Wood, PK, Simpson, LM & Oliver, JD 1987, 'Identification of environmental Vibrio vulnificus isolates with a DNA probe for the cytotoxin-hemolysin gene', Applied and Environmental Microbiology, vol. 53, no. 1, p. 193-195.
Oliver, JD, Roberts, DM, White, VK, Dry, MA & Simpson, LM 1986, 'Bioluminescence in a strain of the human pathogenic bacterium Vibrio vulnificus', Applied and Environmental Microbiology, vol. 52, no. 5, pp. 1209-1211.
Cleland, DR, McDougald, SD & Oliver, JD 1984, 'Substrate degradation and pressure tolerance of free-living and attached bacterial populations in the intestines of shallow-water fish.', Applied and environmental microbiology, vol. 48, no. 6, pp. 1243-1245.
Bacterial populations attached to intestinal linings of shallow-water fish were compared to those free in the lumen for response to hydrostatic pressure and ability to degrade a variety of substrates. Results suggested that, unlike reports on gut-associated deep-sea bacteria, the two shallow-water populations were not significantly different in their pressure or substrate responsiveness.
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.
Kjelleberg, S, McDougald, D, Rasmussen, TB & Givskov, M 2008, 'Quorum sensing inhibition' in Winans, SC & Bassler, BL (eds), Chemical Communication Among Bacteria, pp. 393-416.
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, McDougald, SD & Givskov, M 2007, 'Detection and inhibition of bacterial cell-cell communication' in Bacterial pathogenesis: methods and protocols, Humana Press Inc, Totowa, NJ, pp. 55-68.
Webb, JS, Taylor, M, Rice, SA, Thomas, T, Rao, D, McDougald, D & Kjelleberg, S 2007, 'Biofilms on living surfaces' in Hurst, CJ, Crawford, RL, Garland, JL, Lipson, DA, Mills, AL & Stetzenbach, LD (eds), Manual of Environmental Microbiology, pp. 563-574.
McDougald, D 2006, 'Adaptive Responses of Vibrios' in Thompson, FL, Austin, B & Swings, J (eds), The Biology of Vibrios, pp. 135-157.
Ng, C, Raingeard, D, Chan, A, Steinberg, P & McDougald, D 2012, 'qPCR detection of hepto- and neuro- cyanotoxins in a Singaporean reservoir system', European Society for Comparative Physiology and Biochemistry.
Thompson, FL & Klose, KE 2006, 'Vibrio2005: the First International Conference on the Biology of Vibrios', JOURNAL OF BACTERIOLOGY, AMER SOC MICROBIOLOGY, pp. 4592-4596.View/Download from: Publisher's site
de Nys, R, Rice, SA, Manefield, M, Srinivasan, S, McDougald, D, Loh, A, Ostling, J, Lindum, P, Givskov, M, Steinberg, P & Kjelleberg, S 1998, 'Microbial Biosystems: New Frontiers', 8th International Symposium on Microbial Ecology, Halifax, Canada, pp. 279-285.