I am a Research Group Leader in the ithree institute and founding Director of the Microbial Imaging Facility at UTS. I obtained my BSc (Hons I) in 1989 and PhD in 1994 from the University of Queensland. I obtained postdoctoral training at the University of Queensland (1995-2001) and the University of California, San Francisco, USA (2001-2004). In 2004 I received an NHMRC R Douglas Wright Career Development Award (2004-2008) and returned to Australia to establish my own research group in the Department of Microbiology at Monash University. In 2008 I was recruited to the University of Technology Sydney where I currently lead a research team in the (now) ithree institute. In 2009 I was awarded an NHMRC Senior Research Fellowship. My current research program investigates bacterial lifestyles and their roles in infection and antibiotic resistance. As my research relies heavily on advanced microscopy techniques, I established the Microbial Imaging Facility at UTS to meet these needs. We have rapidly become recognized as world-leaders in the use of super-resolution microscopy techniques to study microbiology. Since joining UTS I have also led the establishment the Microbial Imaging Facility of which I am Director.
My research has produced a number of important paradigm shifts in our understanding of bacterial lifestyles. Many of my published papers have high numbers of citations and continue to be cited.The most significant of these is the article published in 2002 in Science. At the time of publication this was ranked number 1 in "All of Biology" by the Faculty of 1000 and is ranked in the top category as "Exceptional". This paper has promoted a paradigm shift in our understanding of the architecture of bacterial biofilms and demonstrated a novel role for DNA in biology.
Australian Society for Microbiology (FASM)
American Society for Microbiology
My research has produced a number of important paradigm shifts in our understanding of several biological phenomena as outlined below.
Versatility of DNA: We have demonstrated that DNA confers several biological functions that are un-related to its role in coding genetic information. When DNA is situated outside of the confines of the cell it functions as a glue to bind biofilms cells to each other and surfaces, it controls bacterial traffic flow by aligning cells to the overall direction of travel, it provides cohesion between cells to co-ordinate their behaviour and it acts as a sticky substrate for type IV pili binding to enable twitching motility.
The role of stigmergy in how bacteria self-organise multi-cellular activities: Our reserarch provided a greater understanding of how large populations of bacteria self-organise individual behaviours to enable active expansion of biofilm communities. Her studies have revealed that eDNA enables motile bacterial cells to co-ordinate their efforts to build a complex interconnected network of furrows which leads to the manifestation of a striking intricate pattern of trails comprised of densely packed, highly organised, motile bacteria.
Membrane vesicle formation: Membrane vesicle formation from bacteria is important for biofilm development and pathogenesis. Whitchurch’s research has challenged the prevailing dogma that membrane vesicles are produced by blebbing of the outer-membrane. We were the first to capture vesicle formation in live bacterial cells and found that membrane vesicles in biofilms are formed through re-circularisation of membranes produced as a consequence of explosive cell lysis.
Bacterial production of shared resources: The process by which eDNA, moonlighting proteins and other cellular components that function as shared resources, or ‘public goods’, in bacterial communities are produced has been unknown for many bacteria. Many of these ‘public goods’ are important virulence factors. Our research has revealed that explosive cell lysis accounts for the production of these ‘public goods’ and the conserved prophage endolysin is required for explosive cell lysis. It is likely that phage-mediated explosive cell lysis is a ubiquitous process found in many bacterial species as many produce membrane vesicles, moonlighting proteins and a biofilm matrix comprised of eDNA, lipids and cytoplasmic proteins, and the presence of prophage endolysins are a common feature of most bacterial genomes.
Explosive cell lysis in infection and inflammation: While we have established that ECL is required for biofilm development in vitro, its role in infection and inflammation is unknown. To that end, we have assembled a team of experts to test our hypothesis that ECL leads to the release of factors that contribute to immunopathogenic processes. Our model is based around the ability of Pseudomonas aeruginosa to cause acute and chronic respiratory infections. Specifically, we will study immune stimulation and inflammation, programmed cell death pathways, intracellular survival, and inflammasome activation, by using ECL mutant bacteria, and in vitro macrophage and mouse lung infection models.
· Explosive cell lysis and roles in infection, inflammation and biofilm development
· L-form bacteria and roles in infection and antibiotic resistance
· Twitching motility mediated biofilm expansion by P. aeruginosa
· Biofilm formation and migration on implanted medical devices
· Assessment of novel surfaces and compounds for antibiofilm activity
· Molecular microbiology
· Microscopy including super-resolution
· Biofilm models (static, flow, bioreactor)
· Biofilm expansion assays
· Tissue culture infection models - including polarized airway epithelia, biofilm co-culture
· Animal models of infection (worm, Galleria, mouse)
Infection and Immunity
Nolan, LM, McCaughey, LC, Merjane, J, Turnbull, L & Whitchurch, CB 2020, 'ChpC controls twitching motility-mediated expansion of Pseudomonas aeruginosa biofilms in response to serum albumin, mucin and oligopeptides.', Microbiology (Reading, England).View/Download from: Publisher's site
Twitching motility-mediated biofilm expansion occurs via coordinated, multi-cellular collective behaviour to allow bacteria to actively expand across surfaces. Type-IV pili (T4P) are cell-associated virulence factors which mediate twitching motility via rounds of extension, surface attachment and retraction. The Chp chemosensory system is thought to respond to environmental signals to regulate the biogenesis, assembly and twitching motility function of T4P. In other well characterised chemosensory systems, methyl-accepting chemotaxis proteins (MCPs) feed environmental signals through a CheW adapter protein to the histidine kinase CheA to modulate motility. The Pseudomonas aeruginosa Chp system has an MCP PilJ and two CheW adapter proteins, PilI and ChpC, that likely interact with the histidine kinase ChpA to feed environmental signals into the system. In the current study we show that ChpC is involved in the response to host-derived signals serum albumin, mucin and oligopeptides. We demonstrate that these signals stimulate an increase in twitching motility, as well as in levels of 3'-5'-cyclic adenosine monophosphate (cAMP) and surface-assembled T4P. Interestingly, our data shows that changes in cAMP and surface piliation levels are independent of ChpC but that the twitching motility response to these environmental signals requires ChpC. Furthermore, we show that protease activity is required for the twitching motility response of P. aeruginosa to environmental signals. Based upon our data we propose a model whereby ChpC feeds these environmental signals into the Chp system, potentially via PilJ or another MCP, to control twitching motility. PilJ and PilI then modulate T4P surface levels to allow the cell to continue to undergo twitching motility. Our study is the first to link environmental signals to the Chp chemosensory system and refines our understanding of how this system controls twitching motility-mediated biofilm expansion in P. aeruginosa.
Lu, J, Cokcetin, NN, Burke, CM, Turnbull, L, Liu, M, Carter, DA, Whitchurch, CB & Harry, EJ 2019, 'Honey can inhibit and eliminate biofilms produced by Pseudomonas aeruginosa.', Scientific reports, vol. 9, no. 1.View/Download from: Publisher's site
Chronic wound treatment is becoming increasingly difficult and costly, further exacerbated when wounds become infected. Bacterial biofilms cause most chronic wound infections and are notoriously resistant to antibiotic treatments. The need for new approaches to combat polymicrobial biofilms in chronic wounds combined with the growing antimicrobial resistance crisis means that honey is being revisited as a treatment option due to its broad-spectrum antimicrobial activity and low propensity for bacterial resistance. We assessed four well-characterised New Zealand honeys, quantified for their key antibacterial components, methylglyoxal, hydrogen peroxide and sugar, for their capacity to prevent and eradicate biofilms produced by the common wound pathogen Pseudomonas aeruginosa. We demonstrate that: (1) honey used at substantially lower concentrations compared to those found in honey-based wound dressings inhibited P. aeruginosa biofilm formation and significantly reduced established biofilms; (2) the anti-biofilm effect of honey was largely driven by its sugar component; (3) cells recovered from biofilms treated with sub-inhibitory honey concentrations had slightly increased tolerance to honey; and (4) honey used at clinically obtainable concentrations completely eradicated established P. aeruginosa biofilms. These results, together with their broad antimicrobial spectrum, demonstrate that manuka honey-based wound dressings are a promising treatment for infected chronic wounds, including those with P. aeruginosa biofilms.
See-Too, WS, Ambrose, M, Malley, R, Ee, R, Mulcahy, E, Manche, E, Lazenby, J, McEwan, B, Pagnon, J, Chen, JW, Chan, KG, Turnbull, L, Whitchurch, CB & Roddam, LF 2019, 'Pandoraea fibrosis sp. nov., a novel Pandoraea species isolated from clinical respiratory samples.', International journal of systematic and evolutionary microbiology, vol. 69, no. 3, pp. 645-651.View/Download from: Publisher's site
Pandoraea species have been isolated from diverse environmental samples and are emerging important respiratory pathogens, particularly in people with cystic fibrosis (CF). In the present study, two bacterial isolates initially recovered from consecutive sputum samples collected from a CF patient and identified as Pandoraea pnomenusa underwent a polyphasic taxonomic analysis. The isolates were found to be Gram-negative, facultative anaerobic motile bacilli and subsequently designated as strains 6399T (=LMG29626T=DSM103228T) and 7641 (=LMG29627=DSM103229), respectively. Phylogenetic analysis based on 16S rRNA and gyrB gene sequences revealed that 6399T and 7641 formed a distinct phylogenetic lineage within the genus Pandoraea. Genome sequence comparison analysis indicated that strains 6399T and 7641 are clonal and share 100 % similarity, however, similarity to other type strains (ANIb 73.2-88.8 %, ANIm 83.5-89.9 % and OrthoANI 83.2-89.3 %) indicates that 6399T and 7641 do not belong to any of the reported type species. The major cellular fatty acids of 6399T were C16 : 0 (32.1 %) C17 : 0cyclo (18.7 %) and C18 : 1ω7c (14.5 %), while Q-8 was the only respiratory quinone detected. The major polar lipids identified were phosphatidylethanolamine, phosphatidylglycerol and diphosphatidylglycerol. The genomic DNA G+C content of 6399T was 62.9 (mol%). Strain 6399T can be differentiated from other members of Pandoraea by the absence of C19 : 0ω8c cyclo and by the presence of C17 : 0ω8c cyclo. Together our data show that the bacterial strains 6399T and 7641 represent a novel species of the genus Pandoraea, for which the name Pandoraea fibrosis sp. nov. is proposed (type strain 6399T).
Cain, AK, Nolan, LM, Sullivan, GJ, Whitchurch, CB, Filloux, A & Parkhill, J 2019, 'Complete Genome Sequence of Pseudomonas aeruginosa Reference Strain PAK.', Microbiology Resource Announcements, vol. 8, no. 41.View/Download from: Publisher's site
We report the complete genome of Pseudomonas aeruginosa strain PAK, a strain which has been instrumental in the study of a range of P. aeruginosa virulence and pathogenesis factors and has been used for over 50 years as a laboratory reference strain.
Abstract Natural transformation is a mechanism that enables competent bacteria to acquire naked, exogenous DNA from the environment. It is a key process that facilitates the dissemination of antibiotic resistance and virulence determinants throughout bacterial populations. Pseudomonas aeruginosa is an opportunistic Gram-negative pathogen that produces large quantities of extracellular DNA (eDNA) that is required for biofilm formation. P. aeruginosa has a remarkable level of genome plasticity and diversity that suggests a high degree of horizontal gene transfer and recombination but is thought to be incapable of natural transformation. Here we show that P. aeruginosa possesses homologs of all proteins known to be involved in natural transformation in other bacterial species. We found that P. aeruginosa in biofilms is competent for natural transformation of both genomic and plasmid DNA. Furthermore, we demonstrate that type IV pili (T4P) facilitate but are not absolutely essential for natural transformation in P. aeruginosa .
Liu, MY, Cokcetin, NN, Lu, J, Turnbull, L, Carter, DA, Whitchurch, CB & Harry, EJ 2018, 'Rifampicin-Manuka Honey Combinations Are Superior to Other Antibiotic-Manuka Honey Combinations in Eradicating Staphylococcus aureus Biofilms.', Frontiers in Microbiology, vol. 8, pp. 1-12.View/Download from: Publisher's site
Chronic wound infections are a major burden to both society and the health care industry. Bacterial biofilms are the major cause of chronic wound infections and are notoriously recalcitrant to treatments with antibiotics, making them difficult to eradicate. Thus, new approaches are required to combat biofilms in chronic wounds. One possible approach is to use drug combination therapies. Manuka honey has potent broad-spectrum antibacterial activity and has previously shown synergistic activity in combination with antibiotics against common wound pathogens, including Staphylococcus aureus. In addition, manuka honey exhibits anti-biofilm activity, thereby warranting the investigation of its potential as a combination therapy with antibiotics for the topical treatment of biofilm-related infections. Here we report the first use of MacSynergy II to investigate the response of established S. aureus (strain NCTC 8325) biofilms to treatment by combinations of Medihoney (medical grade manuka honey) and conventional antibiotics that are used for preventing or treating infections: rifampicin, oxacillin, fusidic acid, clindamycin, and gentamicin. Using checkerboard microdilution assays, viability assays and MacSynergy II analysis we show that the Medihoney-rifampicin combination was more effective than combinations using the other antibiotics against established staphylococcal biofilms. Medihoney and rifampicin were strongly synergistic in their ability to reduce both biofilm biomass and the viability of embedded S. aureus cells at a level that is likely to be significant in vivo. Other combinations of Medihoney and antibiotic produced an interesting array of effects: Medihoney-fusidic acid treatment showed minor synergistic activity, and Medihoney-clindamycin, -gentamicin, and -oxacillin combinations showed overall antagonistic effects when the honey was used at sub-inhibitory concentration, due to enhanced biofilm formation at these concentrations which could not be counter...
Nolan, LM, Whitchurch, CB, Barquist, L, Katrib, M, Boinett, CJ, Mayho, M, Goulding, D, Charles, IG, Filloux, A, Parkhill, J & Cain, AK 2018, 'A global genomic approach uncovers novel components for twitching motility-mediated biofilm expansion in Pseudomonas aeruginosa', Microbial genomics, vol. 4, no. 11.View/Download from: Publisher's site
Pseudomonas aeruginosa is an extremely successful pathogen able to cause both acute and chronic infections in a range of hosts, utilizing a diverse arsenal of cell-associated and secreted virulence factors. A major cell-associated virulence factor, the Type IV pilus (T4P), is required for epithelial cell adherence and mediates a form of surface translocation termed twitching motility, which is necessary to establish a mature biofilm and actively expand these biofilms. P. aeruginosa twitching motility-mediated biofilm expansion is a coordinated, multicellular behaviour, allowing cells to rapidly colonize surfaces, including implanted medical devices. Although at least 44 proteins are known to be involved in the biogenesis, assembly and regulation of the T4P, with additional regulatory components and pathways implicated, it is unclear how these components and pathways interact to control these processes. In the current study, we used a global genomics-based random-mutagenesis technique, transposon directed insertion-site sequencing (TraDIS), coupled with a physical segregation approach, to identify all genes implicated in twitching motility-mediated biofilm expansion in P. aeruginosa. Our approach allowed identification of both known and novel genes, providing new insight into the complex molecular network that regulates this process in P. aeruginosa. Additionally, our data suggest that the flagellum-associated gene products have a differential effect on twitching motility, based on whether components are intra- or extracellular. Overall the success of our TraDIS approach supports the use of this global genomic technique for investigating virulence genes in bacterial pathogens.
Pingle, H, Wang, P-Y, Cavaliere, R, Whitchurch, CB, Thissen, H & Kingshott, P 2018, 'Minimal attachment of Pseudomonas aeruginosa to DNA modified surfaces.', Biointerphases, vol. 13, no. 6.View/Download from: Publisher's site
Extracellular deoxyribonucleic acid (eDNA) exists in biological environments such as those around medical implants since prokaryotic or eukaryotic cells can undergo processes such as autolysis, necrosis, and apoptosis. For bacteria, eDNA has been shown to be involved in biofilm formation and gene transfer and acts as a nutrient source. In terms of biofilm formation, eDNA in solution has been shown to be very important in increasing attachment; however, very little is known about the role played by surface immobilized eDNA in initiating bacterial attachment and whether the nature of a DNA layer (physically adsorbed or covalently attached, and molecular weight) influences biofilm formation. In this study, the authors shed light on the role that surface attached DNA plays in the early biofilm formation by using Si wafers (Si) and allylamine plasma polymer (AAMpp) coated Si wafers to adsorb and covalently immobilize salmon sperm DNA of three different molecular weights. Pseudomonas aeruginosa was chosen to study the bacterial interactions with these DNA functionalized surfaces. Characterization of surface chemistry and imaging of attached bacteria were performed via x-ray photoelectron spectroscopy (XPS), scanning electron microscopy, and epi-fluorescence microscopy. XPS results confirmed the successful grafting of DNA on the AAMpp and Si surfaces, and surprisingly the results showed that the surface attached DNA actually reduced initial bacterial attachment, which was contrary to the initial hypothesis. This adds speculation about the specific role played by DNA in the dynamics of how it influences biofilm formation, with the possibility that it could actually be used to make bacterial resistant surfaces.
Ranieri, MR, Whitchurch, CB & Burrows, LL 2018, 'Mechanisms of biofilm stimulation by subinhibitory concentrations of antimicrobials.', Current opinion in microbiology, vol. 45, pp. 164-169.View/Download from: Publisher's site
Biofilms are a typical mode of growth for most microorganisms and provide them with a variety of survival benefits. Biofilms can pose medical and industrial challenges due to their increased tolerance of antimicrobials and disinfectants. Exposure of bacteria to subinhibitory concentrations of those compounds can further exacerbate the problem, as they provoke physiological changes that lead to increased biofilm production and potential therapeutic failure. The protected niche of a biofilm provides conditions that promote selection for persisters and resistant mutants. In this review we discuss our current understanding of the mechanisms underlying biofilm stimulation in response to subinhibitory antimicrobials, and how we might exploit this 'anti-antibiotic' phenotype to treat biofilm-related infections and discover new compounds.
Raymond, BBA, Jenkins, C, Turnbull, L, Whitchurch, CB & Djordjevic, SP 2018, 'Extracellular DNA release from the genome-reduced pathogen Mycoplasma hyopneumoniae is essential for biofilm formation on abiotic surfaces.', Scientific reports, vol. 8, no. 1, pp. 10373-10373.View/Download from: Publisher's site
Mycoplasma hyopneumoniae is an economically devastating, globally disseminated pathogen that can maintain a chronic infectious state within its host, swine. Here, we depict the events underpinning M. hyopneumoniae biofilm formation on an abiotic surface and demonstrate for the first time, biofilms forming on porcine epithelial cell monolayers and in the lungs of pigs, experimentally infected with M. hyopneumoniae. Nuclease treatment prevents biofilms forming on glass but not on porcine epithelial cells indicating that extracellular DNA (eDNA), which localises at the base of biofilms, is critical in the formation of these structures on abiotic surfaces. Subpopulations of M. hyopneumoniae cells, denoted by their ability to take up the dye TOTO-1 and release eDNA, were identified. A visually distinct sub-population of pleomorphic cells, that we refer to here as large cell variants (LCVs), rapidly transition from phase dark to translucent "ghost" cells. The translucent cells accumulate the membrane-impermeable dye TOTO-1, forming readily discernible membrane breaches immediately prior to lysis and the possible release of eDNA and other intracellular content (public goods) into the extracellular environment. Our novel observations expand knowledge of the lifestyles adopted by this wall-less, genome-reduced pathogen and provide further insights to its survival within farm environments and swine.
Raymond, BBA, Madhkoor, R, Schleicher, I, Uphoff, CC, Turnbull, L, Whitchurch, CB, Rohde, M, Padula, MP & Djordjevic, SP 2018, 'Extracellular Actin Is a Receptor for Mycoplasma hyopneumoniae.', Frontiers in cellular and infection microbiology, vol. 8, no. Feb.View/Download from: Publisher's site
Mycoplasma hyopneumoniae, an agriculturally important porcine pathogen, disrupts the mucociliary escalator causing ciliostasis, loss of cilial function, and epithelial cell death within the porcine lung. Losses to swine production due to growth rate retardation and reduced feed conversion efficiency are severe, and antibiotics are used heavily to control mycoplasmal pneumonia. Notably, little is known about the repertoire of host receptors that M. hyopneumoniae targets to facilitate colonization. Here we show, for the first time, that actin exists extracellularly on porcine epithelial monolayers (PK-15) using surface biotinylation and 3D-Structured Illumination Microscopy (3D-SIM), and that M. hyopneumoniae binds to the extracellular β-actin exposed on the surface of these cells. Consistent with this hypothesis we show: (i) monoclonal antibodies that target β-actin significantly block the ability of M. hyopneumoniae to adhere and colonize PK-15 cells; (ii) microtiter plate binding assays show that M. hyopneumoniae cells bind to monomeric G-actin in a dose dependent manner; (iii) more than 100 M. hyopneumoniae proteins were recovered from affinity-chromatography experiments using immobilized actin as bait; and (iv) biotinylated monomeric actin binds directly to M. hyopneumoniae proteins in ligand blotting studies. Specifically, we show that the P97 cilium adhesin possesses at least two distinct actin-binding regions, and binds monomeric actin with nanomolar affinity. Taken together, these observations suggest that actin may be an important receptor for M. hyopneumoniae within the swine lung and will aid in the future development of intervention strategies against this devastating pathogen. Furthermore, our observations have wider implications for extracellular actin as an important bacterial receptor.
Raymond, BBA, Turnbull, L, Jenkins, C, Madhkoor, R, Schleicher, I, Uphoff, CC, Whitchurch, CB, Rohde, M & Djordjevic, SP 2018, 'Mycoplasma hyopneumoniae resides intracellularly within porcine epithelial cells.', Scientific reports, vol. 8, no. 1.View/Download from: Publisher's site
Enzootic pneumonia incurs major economic losses to pork production globally. The primary pathogen and causative agent, Mycoplasma hyopneumoniae, colonises ciliated epithelium and disrupts mucociliary function predisposing the upper respiratory tract to secondary pathogens. Alleviation of disease is reliant on antibiotics, vaccination, and sound animal husbandry, but none are effective at eliminating M. hyopneumoniae from large production systems. Sustainable pork production systems strive to lower reliance on antibiotics but lack of a detailed understanding of the pathobiology of M. hyopneumoniae has curtailed efforts to develop effective mitigation strategies. M. hyopneumoniae is considered an extracellular pathogen. Here we show that M. hyopneumoniae associates with integrin β1 on the surface of epithelial cells via interactions with surface-bound fibronectin and initiates signalling events that stimulate pathogen uptake into clathrin-coated vesicles (CCVs) and caveosomes. These early events allow M. hyopneumoniae to exploit an intracellular lifestyle by commandeering the endosomal pathway. Specifically, we show: (i) using a modified gentamicin protection assay that approximately 8% of M. hyopneumoniae cells reside intracellularly; (ii) integrin β1 expression specifically co-localises with the deposition of fibronectin precisely where M. hyopneumoniae cells assemble extracellularly; (iii) anti-integrin β1 antibodies block entry of M. hyopneumoniae into porcine cells; and (iv) M. hyopneumoniae survives phagolysosomal fusion, and resides within recycling endosomes that are trafficked to the cell membrane. Our data creates a paradigm shift by challenging the long-held view that M. hyopneumoniae is a strict extracellular pathogen and calls for in vivo studies to determine if M. hyopneumoniae can traffic to extrapulmonary sites in commercially-reared pigs.
Bitto, NJ, Chapman, R, Pidot, S, Costin, A, Lo, C, Choi, J, D'Cruze, T, Reynolds, EC, Dashper, SG, Turnbull, L, Whitchurch, CB, Stinear, TP, Stacey, KJ & Ferrero, RL 2017, 'Bacterial membrane vesicles transport their DNA cargo into host cells.', Scientific Reports, vol. 7, no. 1, pp. 1-11.View/Download from: Publisher's site
Bacterial outer membrane vesicles (OMVs) are extracellular sacs containing biologically active products, such as proteins, cell wall components and toxins. OMVs are reported to contain DNA, however, little is known about the nature of this DNA, nor whether it can be transported into host cells. Our work demonstrates that chromosomal DNA is packaged into OMVs shed by bacteria during exponential phase. Most of this DNA was present on the external surfaces of OMVs, with smaller amounts located internally. The DNA within the internal compartments of Pseudomonas aeruginosa OMVs were consistently enriched in specific regions of the bacterial chromosome, encoding proteins involved in virulence, stress response, antibiotic resistance and metabolism. Furthermore, we demonstrated that OMVs carry DNA into eukaryotic cells, and this DNA was detectable by PCR in the nuclear fraction of cells. These findings suggest a role for OMV-associated DNA in bacterial-host cell interactions and have implications for OMV-based vaccines.
Rabi, R, Turnbull, L, Whitchurch, CB, Awad, M & Lyras, D 2017, 'Structural Characterization of Clostridium sordellii Spores of Diverse Human, Animal, and Environmental Origin and Comparison to Clostridium difficile Spores.', mSphere, vol. 2, no. 5, pp. 1-12.View/Download from: Publisher's site
Clostridium sordellii is an often-lethal bacterium causing human and animal disease. Crucial to the infectious cycle of C. sordellii is its ability to produce spores, which can germinate into toxin-producing vegetative bacteria under favorable conditions. However, structural details of the C. sordellii spore are lacking. Here, we used a range of electron microscopy techniques together with superresolution optical microscopy to characterize the C. sordellii spore morphology with an emphasis on the exosporium. The C. sordellii spore is made up of multiple layers with the exosporium presenting as a smooth balloon-like structure that is open at the spore poles. Focusing on the outer spore layers, we compared the morphologies of C. sordellii spores derived from different strains and determined that there is some variation between the spores, most notably with spores of some strains having tubular appendages. Since Clostridium difficile is a close relative of C. sordellii, their spores were compared by electron microscopy and their exosporia were found to be distinctly different from each other. This study therefore provides new structural details of the C. sordellii spore and offers insights into the physical structure of the exosporium across clostridial species. IMPORTANCEClostridium sordellii is a significant pathogen with mortality rates approaching 100%. It is the bacterial spore that is critical in initiating infection and disease. An understanding of spore structures as well as spore morphology across a range of strains may lead to a better understanding of C. sordellii infection and disease. However, the structural characteristics of the C. sordellii spores are limited. In this work, we have addressed this lack of detail and characterized the C. sordellii spore morphology. The use of traditional and advanced microscopy techniques has provided detailed new observations of C. sordellii spore structural features, which serve as a reference point for structural st...
Vallotton, P, van Oijen, AM, Whitchurch, CB, Gelfand, V, Yeo, L, Tsiavaliaris, G, Heinrich, S, Dultz, E, Weis, K & Grünwald, D 2017, 'Diatrack particle tracking software: Review of applications and performance evaluation', Traffic, vol. 18, no. 12, pp. 840-852.View/Download from: Publisher's site
© 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd Object tracking is an instrumental tool supporting studies of cellular trafficking. There are three challenges in object tracking: the identification of targets; the precise determination of their position and boundaries; and the assembly of correct trajectories. This last challenge is particularly relevant when dealing with densely populated images with low signal-to-noise ratios—conditions that are often encountered in applications such as organelle tracking, virus particle tracking or single-molecule imaging. We have developed a set of methods that can handle a wide variety of signal complexities. They are compiled into a free software package called Diatrack. Here we review its main features and utility in a range of applications, providing a survey of the dynamic imaging field together with recommendations for effective use. The performance of our framework is shown to compare favorably to a wide selection of custom-developed algorithms, whether in terms of localization precision, processing speed or correctness of tracks.
Trussart, M, Yus, E, Martinez, S, Baù, D, Tahara, YO, Pengo, T, Widjaja, M, Kretschmer, S, Swoger, J, Djordjevic, S, Turnbull, L, Whitchurch, C, Miyata, M, Marti-Renom, MA, Lluch-Senar, M & Serrano, L 2017, 'Defined chromosome structure in the genome-reduced bacterium Mycoplasma pneumoniae.', Nature Communications, vol. 8.View/Download from: Publisher's site
DNA-binding proteins are central regulators of chromosome organization; however, in genome-reduced bacteria their diversity is largely diminished. Whether the chromosomes of such bacteria adopt defined three-dimensional structures remains unexplored. Here we combine Hi-C and super-resolution microscopy to determine the structure of the Mycoplasma pneumoniae chromosome at a 10 kb resolution. We find a defined structure, with a global symmetry between two arms that connect opposite poles, one bearing the chromosomal Ori and the other the midpoint. Analysis of local structures at a 3 kb resolution indicates that the chromosome is organized into domains ranging from 15 to 33 kb. We provide evidence that genes within the same domain tend to be co-regulated, suggesting that chromosome organization influences transcriptional regulation, and that supercoiling regulates local organization. This study extends the current understanding of bacterial genome organization and demonstrates that a defined chromosomal structure is a universal feature of living systems.
Collective behavior of bacterial colonies plays critical roles in adaptability, survivability, biofilm expansion and infection. We employ an individual-based model of an interstitial biofilm to study emergent pattern formation based on the assumptions that rod-shaped bacteria furrow through a viscous environment and excrete extracellular polymeric substances which bias their rate of motion. Because the bacteria furrow through their environment, the substratum stiffness is a key control parameter behind the formation of distinct morphological patterns. By systematically varying this property (which we quantify with a stiffness coefficient γ), we show that subtle changes in the substratum stiffness can give rise to a stable state characterized by a high degree of local order and long-range pattern formation. The ordered state exhibits characteristics typically associated with bacterial fitness advantages, even though it is induced by changes in environmental conditions rather than changes in biological parameters. Our findings are applicable to a broad range of biofilms and provide insights into the relationship between bacterial movement and their environment, and basic mechanisms behind self-organization of biophysical systems.
Zachreson, C, Yap, X, Gloag, ES, Shimoni, R, Whitchurch, CB & Toth, M 2017, 'Network patterns in exponentially growing two-dimensional biofilms.', Physical Review E, vol. 96, no. 4-1, pp. 042401-042401.View/Download from: Publisher's site
Anisotropic collective patterns occur frequently in the morphogenesis of two-dimensional biofilms. These patterns are often attributed to growth regulation mechanisms and differentiation based on gradients of diffusing nutrients and signaling molecules. Here, we employ a model of bacterial growth dynamics to show that even in the absence of growth regulation or differentiation, confinement by an enclosing medium such as agar can itself lead to stable pattern formation over time scales that are employed in experiments. The underlying mechanism relies on path formation through physical deformation of the enclosing environment.
Gloag, ES, Elbadawi, C, Zachreson, CJ, Aharonovich, I, Toth, M, Charles, IG, Turnbull, L & Whitchurch, CB 2017, 'Micro-Patterned Surfaces That Exploit Stigmergy to Inhibit Biofilm Expansion.', Frontiers in Microbiology, vol. 7, pp. 1-10.View/Download from: Publisher's site
Twitching motility is a mode of surface translocation that is mediated by the extension and retraction of type IV pili and which, depending on the conditions, enables migration of individual cells or can manifest as a complex multicellular collective behavior that leads to biofilm expansion. When twitching motility occurs at the interface of an abiotic surface and solidified nutrient media, it can lead to the emergence of extensive self-organized patterns of interconnected trails that form as a consequence of the actively migrating bacteria forging a furrow network in the substratum beneath the expanding biofilm. These furrows appear to direct bacterial movements much in the same way that roads and footpaths coordinate motor vehicle and human pedestrian traffic. Self-organizing systems such as these can be accounted for by the concept of stigmergy which describes self-organization that emerges through indirect communication via persistent signals within the environment. Many bacterial communities are able to actively migrate across solid and semi-solid surfaces through complex multicellular collective behaviors such as twitching motility and flagella-mediated swarming motility. Here, we have examined the potential of exploiting the stigmergic behavior of furrow-mediated trail following as a means of controlling bacterial biofilm expansion along abiotic surfaces. We found that incorporation of a series of parallel micro-fabricated furrows significantly impeded active biofilm expansion by Pseudomonas aeruginosa and Proteus vulgaris. We observed that in both cases bacterial movements tended to be directed along the furrows. We also observed that narrow furrows were most effective at disrupting biofilm expansion as they impeded the ability of cells to self-organize into multicellular assemblies required for escape from the furrows and migration into new territory. Our results suggest that the implementation of micro-fabricated furrows that exploit stigmergy may be a ...
Turnbull, L, Toyofuku, M, Hynen, AL, Kurosawa, M, Pessi, G, Petty, NK, Osvath, SR, Carcamo-Oyarce, G, Gloag, ES, Shimoni, R, Omasits, U, Ito, S, Yap, X, Monahan, LG, Cavaliere, R, Ahrens, CH, Charles, IG, Nomura, N, Eberl, L & Whitchurch, CB 2016, 'Explosive cell lysis as a mechanism for the biogenesis of bacterial membrane vesicles and biofilms', NATURE COMMUNICATIONS, vol. 7.View/Download from: Publisher's site
McCaughey, LC, Josts, I, Grinter, R, White, P, Byron, O, Tucker, NP, Matthews, JM, Kleanthous, C, Whitchurch, CB & Walker, D 2016, 'Discovery, characterization and in vivo activity of pyocin SD2, a protein antibiotic from Pseudomonas aeruginosa', BIOCHEMICAL JOURNAL, vol. 473, pp. 2345-2358.View/Download from: Publisher's site
Gloag, ES, Turnbull, L, Javed, MA, Wang, H, Gee, ML, Wade, SA & Whitchurch, CB 2016, 'Stigmergy co-ordinates multicellular collective behaviours during Myxococcus xanthus surface migration', SCIENTIFIC REPORTS, vol. 6.View/Download from: Publisher's site
Loo, CY, Rohanizadeh, R, Young, PM, Traini, D, Cavaliere, R, Whitchurch, CB & Lee, WH 2016, 'Combination of Silver Nanoparticles and Curcumin Nanoparticles for Enhanced Anti-biofilm Activities.', Journal of agricultural and food chemistry, vol. 64, pp. 2513-2522.View/Download from: Publisher's site
Biofilm tolerance has become a serious clinical concern in the treatment of nosocomial pneumonia owing to the resistance to various antibiotics. There is an urgent need to develop alternative antimicrobial agents or combination drug therapies that are effective via different mechanisms. Silver nanoparticles (AgNPs) have been developed as an anti-biofilm agent for the treatment of infections associated with the use of mechanical ventilations, such as endotracheal intubation. Meanwhile curcumin, a phenolic plant extract, has displayed natural anti-biofilm properties through the inhibition of bacterial quorum sensing systems. The aim of this study was to investigate the possible synergistic/additive interactions of AgNPs and curcumin nanoparticles (Cur-NPs) against both Gram-negative (Pseudomonas aeruginosa) and Gram-positive (Staphylococcus aureus) microorganisms. The combination of AgNPs and Cur-NPs (termed Cur-SNPs) at 100 μg/mL disrupted 50% of established bacterial biofilms (formed on microtiter plates). However, further increase in the concentration of Cur-SNPs failed to effectively eliminate the biofilms. To achieve the same effect, at least 500 μg/mL Cur-NP alone was needed. Scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) revealed that combination therapy (Cur-SNPs) was the most potent to eradicate preformed biofilm compared to monodrug therapy. These agents are also nontoxic to healthy human bronchial epithelial cells (BEAS2B).
Redpath, GM, Sophocleous, RA, Turnbull, L, Whitchurch, CB & Cooper, ST 2016, 'Ferlins show tissue-specific expression and segregate as plasma membrane/late endosomal or trans-Golgi/recycling ferlins.', Traffic, vol. 17, no. 3, pp. 245-266.View/Download from: Publisher's site
Ferlins are a family of transmembrane-anchored vesicle fusion proteins uniquely characterized by 5-7 tandem cytoplasmic C2 domains, Ca(2+) -regulated phospholipid-binding domains that regulate vesicle fusion in the synaptotagmin family. In humans, dysferlin mutations cause limb-girdle muscular dystrophy (LGMD2B) due to defective Ca(2+) -dependent, vesicle-mediated membrane repair and otoferlin mutations cause non-syndromic deafness due to defective Ca(2+) -triggered auditory neurotransmission. In this study, we describe the tissue-specific expression, subcellular localization and endocytic trafficking of the ferlin family. Dysferlin, myoferlin, and Fer1L6 are plasma membrane (PM) ferlins, whereas otoferlin and Fer1L5 localize predominantly to intracellular compartments. Studies of endosomal transit together with 3D-structured illumination microscopy reveals dysferlin and myoferlin are abundantly expressed at the PM and cycle to Rab7-positive late endosomes, supporting potential roles in the late-endosomal pathway. In contrast, Fer1L6 shows concentrated localization to a specific compartment of the trans-Golgi/recycling endosome, cycling rapidly between this compartment and the PM via Rab11 recycling endosomes. Otoferlin also shows trans-Golgi to PM cycling, with very low levels of PM otoferlin suggesting either brief plasma membrane residence, or rare incorporation of otoferlin molecules into the PM. Thus, type-I and type-II ferlins segregate as PM/late-endosomal or trans-Golgi/recycling ferlins, consistent with different ferlins mediating vesicle fusion events in specific subcellular locations.
Duggin, IG, Aylett, CHS, Walsh, JC, Michie, KA, Wang, Q, Turnbull, L, Dawson, EM, Harry, EJ, Whitchurch, CB, Amos, LA & Loewe, J 2015, 'CetZ tubulin-like proteins control archaeal cell shape', NATURE, vol. 519, no. 7543, pp. 362-+.View/Download from: Publisher's site
Gloag, ES, Turnbull, L & Whitchurch, CB 2015, 'Bacterial stigmergy: an organising principle of multicellular collective behaviours of bacteria.', Scientifica, vol. 2015, pp. 1-9.View/Download from: Publisher's site
The self-organisation of collective behaviours often manifests as dramatic patterns of emergent large-scale order. This is true for relatively "simple" entities such as microbial communities and robot "swarms," through to more complex self-organised systems such as those displayed by social insects, migrating herds, and many human activities. The principle of stigmergy describes those self-organised phenomena that emerge as a consequence of indirect communication between individuals of the group through the generation of persistent cues in the environment. Interestingly, despite numerous examples of multicellular behaviours of bacteria, the principle of stigmergy has yet to become an accepted theoretical framework that describes how bacterial collectives self-organise. Here we review some examples of multicellular bacterial behaviours in the context of stigmergy with the aim of bringing this powerful and elegant self-organisation principle to the attention of the microbial research community.
Kennan, RM, Lovitt, CJ, Han, X, Parker, D, Turnbull, L, Whitchurch, CB & Rood, JI 2015, 'A two-component regulatory system modulates twitching motility in Dichelobacter nodosus', Veterinary Microbiology, vol. 179, no. 1-2, pp. 34-41.View/Download from: Publisher's site
Dichelobacter nodosus is the essential causative agent of footrot in sheep and type IV fimbriae-mediated twitching motility has been shown to be essential for virulence. We have identified a two-component signal transduction system (TwmSR) that shows similarity to chemosensory systems from other bacteria. Insertional inactivation of the gene encoding the response regulator, TwmR, led to a twitching motility defect, with the mutant having a reduced rate of twitching motility when compared to the wild-type and a mutant complemented with the wild-type twmR gene. The reduced rate of twitching motility was not a consequence of a reduced growth rate or decreased production of surface located fimbriae, but video microscopy indicated that it appeared to result from an overall loss of twitching directionality. These results suggest that a chemotactic response to environmental factors may play an important role in the D. nodosus-mediated disease process.
Liu, M, Lu, J, Mueller, P, Turnbull, L, Burke, CM, Schlothauer, RC, Carter, DA, Whitchurch, CB & Harry, EJ 2015, 'Antibiotic-specific differences in the response of Staphylococcus aureus to treatment with antimicrobiala combined with manuka honey', Frontiers in Microbiology, vol. 5, pp. 1-9.View/Download from: Publisher's site
Skin infections caused by antibiotic resistant Staphylococcus aureus are a significant health problem worldwide; often associated with high treatment cost and mortality rate. Complex natural products like New Zealand (NZ) manuka honey have been revisited and studied extensively as an alternative to antibiotics due to their potent broad-spectrum antimicrobial activity, and the inability to isolate honey-resistant S. aureus. Previous studies showing synergistic effects between manuka-type honeys and antibiotics have been demonstrated against the growth of one methicillin-resistant S. aureus (MRSA) strain. We have previously demonstrated strong synergistic activity between NZ manuka-type honey and rifampicin against growth and biofilm formation of multiple S. arueus strains. Here, we have expanded our investigation using multiple S. aureus strains and four different antibiotics commonly used to treat S. aureus-related skin infections: rifampicin, oxacillin, gentamicin, and clindamycin. Using checkerboard microdilution and agar diffusion assays with S. aureus strains including clinical isolates and MRSA we demonstrate that manuka-type honey combined with these four antibiotics frequently produces a synergistic effect. In some cases when synergism was not observed, there was a significant enhancement in antibiotic susceptibility. Some strains that were highly resistant to an antibiotic when present alone become sensitive to clinically achievable concentrations when combined with honey. However, not all of the S. aureus strains tested responded in the same way to these combinational treatments. Our findings support the use of NZ manuka-type honeys in clinical treatment against S. aureus-related infections and extend their potential use as an antibiotic adjuvant in combinational therapy. Our data also suggest that manuka-type honeys may not work as antibiotic adjuvants for all strains of S. aureus, and this may help determine the mechanistic processes behind honey syner...
Loo, C-Y, Lee, W-H, Young, PM, Cavaliere, R, Whitchurch, CB & Rohanizadeh, R 2015, 'Implications and emerging control strategies for ventilator-associated infections', EXPERT REVIEW OF ANTI-INFECTIVE THERAPY, vol. 13, no. 3, pp. 379-393.View/Download from: Publisher's site
Loo, J, Lee, W-H, Young, PM, Traini, D, Cavaliere, R, Whitchurch, CB & Rohanizadeh, R 2015, 'CURCUMIN AND SILVER NANOPARTICLE HYDROGELS FOR ENDOTRACHEAL TUBE-ASSOCIATED INFECTIONS: CHARACTERIZATION AND ANTI-BIOFILM ACTIVITIES', JOURNAL OF AEROSOL MEDICINE AND PULMONARY DRUG DELIVERY, vol. 28, no. 3, pp. A15-A15.
Nolan, LM, Cavaliere, R, Turnbull, L & Whitchurch, CB 2015, 'Extracellular ATP inhibits twitching motility-mediated biofilm expansion by Pseudomonas aeruginosa.', BMC Microbiology, vol. 15, pp. 1-12.View/Download from: Publisher's site
Pseudomonas aeruginosa is an opportunistic pathogen that exploits damaged epithelia to cause infection. Type IV pili (tfp) are polarly located filamentous structures which are the major adhesins for attachment of P. aeruginosa to epithelial cells. The extension and retraction of tfp powers a mode of surface translocation termed twitching motility that is involved in biofilm development and also mediates the active expansion of biofilms across surfaces. Extracellular adenosine triphosphate (eATP) is a key "danger" signalling molecule that is released by damaged epithelial cells to alert the immune system to the potential presence of pathogens. As P. aeruginosa has a propensity for infecting damaged epithelial tissues we have explored the influence of eATP on tfp biogenesis and twitching motility-mediated biofilm expansion by P. aeruginosa.In this study we have found that eATP inhibits P. aeruginosa twitching motility-mediated expansion of interstitial biofilms at levels that are not inhibitory to growth. We have determined that eATP does not inhibit expression of the tfp major subunit, PilA, but reduces the levels of surface assembled tfp. We have also determined that the active twitching zone of expanding P. aeruginosa interstitial biofilms contain large quantities of eATP which may serve as a signalling molecule to co-ordinate cell movements in the expanding biofilm. The inhibition of twitching motility-mediated interstitial biofilm expansion requires eATP hydrolysis and does not appear to be mediated by the Chp chemosensory system.Endogenous eATP produced by P. aeruginosa serves as a signalling molecule to co-ordinate complex multicellular behaviours of this pathogen. Given the propensity for P. aeruginosa to infect damaged epithelial tissues, our observations suggest that eATP released by damaged cells may provide a cue to reduce twitching motility of P. aeruginosa in order to establish infection at the site of damage. Furthermore, eATP produced by P. aerugino...
Raymond, BBA, Jenkins, C, Seymour, LM, Tacchi, JL, Widjaja, M, Jarocki, VM, Deutscher, AT, Turnbull, L, Whitchurch, CB, Padula, MP & Djordjevic, SP 2015, 'Proteolytic processing of the cilium adhesin MHJ_0194 (P123(J)) in Mycoplasma hyopneumoniae generates a functionally diverse array of cleavage fragments that bind multiple host molecules', CELLULAR MICROBIOLOGY, vol. 17, no. 3, pp. 425-444.View/Download from: Publisher's site
Chaiyadet, S, Smout, M, Johnson, M, Whitchurch, C, Turnbull, L, Kaewkes, S, Sotillo, J, Loukas, A & Sripa, B 2015, 'Excretory/secretory products of the carcinogenic liver fluke are endocytosed by human cholangiocytes and drive cell proliferation and IL6 production', INTERNATIONAL JOURNAL FOR PARASITOLOGY, vol. 45, no. 12, pp. 773-781.View/Download from: Publisher's site
Chaiyadet, S, Sotillo, J, Smout, M, Cantacessi, C, Jones, MK, Johnson, MS, Turnbull, L, Whitchurch, CB, Potriquet, J, Laohaviroj, M, Mulvenna, J, Brindley, PJ, Bethony, JM, Laha, T, Sripa, B & Loukas, A 2015, 'Carcinogenic Liver Fluke Secretes Extracellular Vesicles That Promote Cholangiocytes to Adopt a Tumorigenic Phenotype', JOURNAL OF INFECTIOUS DISEASES, vol. 212, no. 10, pp. 1636-1645.View/Download from: Publisher's site
Smout, MJ, Sotillo, J, Laha, T, Papatpremsiri, A, Rinaldi, G, Pimenta, RN, Chan, LY, Johnson, MS, Turnbull, L, Whitchurch, CB, Giacomin, PR, Moran, CS, Golledge, J, Sripa, B, Mulvenna, JP, Brindley, PJ & Loukas, A 2015, 'Carcinogenic Parasite Secretes Growth Factor That Accelerates Wound Healing and Potentially Promotes Neoplasia', PLoS Pathogens, vol. 11, no. 10.View/Download from: Publisher's site
Infection with the human liver fluke Opisthorchis viverrini induces cancer of the bile ducts, cholangiocarcinoma (CCA). Injury from feeding activities of this parasite within the human biliary tree causes extensive lesions, wounds that undergo protracted cycles of healing, and re-injury over years of chronic infection. We show that O. viverrini secreted proteins accelerated wound resolution in human cholangiocytes, an outcome that was compromised following silencing of expression of the fluke-derived gene encoding the granulin-like growth factor, Ov-GRN-1. Recombinant Ov-GRN-1 induced angiogenesis and accelerated mouse wound healing. Ov-GRN-1 was internalized by human cholangiocytes and induced gene and protein expression changes associated with wound healing and cancer pathways. Given the notable but seemingly paradoxical properties of liver fluke granulin in promoting not only wound healing but also a carcinogenic microenvironment, Ov-GRN-1 likely holds marked potential as a therapeutic wound-healing agent and as a vaccine against an infection-induced cancer of major public health significance in the developing world.
Lu, J, Turnbull, L, Burke, CM, Liu, MY, Carter, DA, Schlothauer, RC, Whitchurch, CB & Harry, L 2014, 'Manuka-type honeys can eradicate biofilms produced by Staphylococcus aureus strains with different biofilm-forming abilities', PeerJ, vol. 2.View/Download from: Publisher's site
Chronic wounds are a major global health problem. Their management is difficult and costly, and the development of antibiotic resistance by both planktonic and biofilm-associated bacteria necessitates the use of alternative wound treatments. Honey is now being revisited as an alternative treatment due to its broad-spectrum antibacterial activity and the inability of bacteria to develop resistance to it. Many previous antibacterial studies have used honeys that are not well characterized, even in terms of quantifying the levels of the major antibacterial components present, making it difficult to build an evidence base for the efficacy of honey as an antibiofilm agent in chronic wound treatment. Here we show that a range of well-characterized New Zealand manuka-type honeys, in which two principle antibacterial components, methylglyoxal and hydrogen peroxide, were quantified, can eradicate biofilms of a range of Staphylococcus aureus strains that differ widely in their biofilm-forming abilities. Using crystal violet and viability assays, along with confocal laser scanning imaging, we demonstrate that in all S. aureus strains, including methicillin-resistant strains, the manuka-type honeys showed significantly higher anti-biofilm activity than clover honey and an isotonic sugar solution. We observed higher anti-biofilm activity as the proportion of manuka-derived honey, and thus methylglyoxal, in a honey blend increased. However, methylglyoxal on its own, or with sugar, was not able to effectively eradicate S. aureus biofilms. We also demonstrate that honey was able to penetrate through the biofilm matrix and kill the embedded cells in some cases. As has been reported for antibiotics, sub-inhibitory concentrations of honey improved biofilm formation by some S. aureus strains, however, biofilm cell suspensions recovered after honey treatment did not develop resistance towards manuka-type honeys. New Zealand manuka-type honeys, at the concentrations they can be applie...
Cavaliere, R, Ball, JL, Turnbull, L & Whitchurch, CB 2014, 'The biofilm matrix destabilizers, EDTA and DNaseI, enhance the susceptibility of nontypeable Hemophilus influenzae biofilms to treatment with ampicillin and ciprofloxacin', Microbiology Open, vol. 3, no. 4, pp. 557-567.View/Download from: Publisher's site
Nontypeable Hemophilus influenzae (NTHi) is a Gram-negative bacterial pathogen that causes chronic biofilm infections of the ears and airways. The biofilm matrix provides structural integrity to the biofilm and protects biofilm cells from antibiotic exposure by reducing penetration of antimicrobial compounds into the biofilm. Extracellular DNA (eDNA) has been found to be a major matrix component of biofilms formed by many species of Gram-positive and Gram-negative bacteria, including NTHi. Interestingly, the cation chelator ethylenediaminetetra-acetic acid (EDTA) has been shown to reduce the matrix strength of biofilms of several bacterial species as well as to have bactericidal activity against various pathogens. EDTA exerts its antimicrobial activity by chelating divalent cations necessary for growth and membrane stability and by destabilizing the matrix thus enhancing the detachment of bacterial cells from the biofilm. In this study, we have explored the role of divalent cations in NTHi biofilm development and stability. We have utilized in vitro static and continuous flow models of biofilm development by NTHi to demonstrate that magnesium cations enhance biofilm formation by NTHi. We found that the divalent cation chelator EDTA is effective at both preventing NTHi biofilm formation and at treating established NTHi biofilms. Furthermore, we found that the matrix destablilizers EDTA and DNaseI increase the susceptibility of NTHi biofilms to ampicillin and ciprofloxacin. Our observations indicate that DNaseI and EDTA enhance the efficacy of antibiotic treatment of NTHi biofilms. These observations may lead to new strategies that will improve the treatment options available to patients with chronic NTHi infections.
Loo, C-Y, Young, PM, Cavaliere, R, Whitchurch, CB, Lee, W-H & Rohanizadeh, R 2014, 'Silver nanoparticles enhance Pseudomonas aeruginosa PAO1 biofilm detachment', DRUG DEVELOPMENT AND INDUSTRIAL PHARMACY, vol. 40, no. 6, pp. 719-729.View/Download from: Publisher's site
Loo, C-Y, Young, PM, Lee, W-H, Cavaliere, R, Whitchurch, CB & Rohanizadeh, R 2014, 'Non-cytotoxic silver nanoparticle-polyvinyl alcohol hydrogels with anti-biofilm activity: designed as coatings for endotracheal tube materials', Biofouling, vol. 30, no. 7, pp. 773-788.View/Download from: Publisher's site
Endotracheal intubation is commonly associated with hospital-acquired infections as the intubation device acts as reservoir for bacterial colonization in the lungs. To reduce the incidence of bacterial colonization on the tubes, hydrogel coatings loaded with antimicrobial agents are gaining popularity. The aim of this study was to incorporate silver nanoparticles (AgNPs) into polyvinyl alcohol (PVA) to form stable hydrogels. Embedding AgNPs into PVA resulted in a decreased elongation at break and an increased tensile strength compared to PVA alone. The Ag release profile varied as a function of the degree of hydrolysis of PVA: the higher degree of hydrolysis demonstrated a lower release rate. Fourier infrared transform spectroscopy demonstrated that AgNPs interacted exclusively with the –OH groups of PVA. AgNP-loaded PVA was non-toxic against human normal bronchial epithelial cells while effective against the attachment of Pseudomonas aeruginosa and Staphylococcus aureus with a greater effect on P. aeruginosa.
Loo, C-Y, Young, PM, Lee, W-H, Traini, D, Cavaliere, R, Whitchurch, CB & Rohanizadeh, R 2014, 'COMBINATION THERAPY OF CURCUMIN AND SILVER NANOPARTICLES WITH ENHANCED ANTI-BIOFILM ACTIVITY FOR TREATMENT OF ENDOTRACHEAL TUBE-ASSOCIATED INFECTIONS', JOURNAL OF AEROSOL MEDICINE AND PULMONARY DRUG DELIVERY, vol. 27, no. 4, pp. A17-A18.
Monahan, LG, Turnbull, L, Osvath, SR, Birch, D, Charles, IG & Whitchurch, CB 2014, 'Rapid conversion of Pseudomonas aeruginosa to a spherical cell morphotype facilitates tolerance to carbapenems and penicillins but increases susceptibility to antimicrobial peptides', Antimicrobial Agents and Chemotherapy, vol. 58, no. 4, pp. 1956-1962.View/Download from: Publisher's site
The Gram negative human pathogen Pseudomonas aeruginosa is able to tolerate high concentrations of ß-lactam antibiotics. Despite inhibiting the growth of the organism, these cell wall-targeting drugs exhibit remarkably little bactericidal activity. However, the mechanisms underlying ß-lactam tolerance are currently unclear. Here we show that P. aeruginosa undergoes a rapid en masse transition from normal rod shaped cells to viable, cell wall defective spherical cells when treated with ß-lactams from the widely used carbapenem and penicillin classes. When the antibiotic is removed, the entire population of spherical cells quickly converts back to the normal bacillary form. Our results demonstrate that these rapid population-wide cell morphotype transitions function as a strategy to survive antibiotic exposure. Taking advantage of these findings, we have developed a novel approach to efficiently kill P. aeruginosa by using carbapenem treatment to induce en masse transition to the spherical cell morphotype and then exploiting the relative fragility and sensitivity of these cells to killing by antimicrobial peptides (AMPs) that are relatively inactive against P. aeruginosa bacillary cells. This approach could broaden the repertoire of antimicrobial compounds used to treat P. aeruginosa and serve as a basis for developing new therapeutics to combat bacterial infections.
Turnbull, L & Whitchurch, CB 2014, 'Motility assays: twitching motility', Methods in Molecular Biology, vol. 1149, no. 1.
Twitching motility is a mode of solid surface translocation that occurs under humid conditions on semisolid or solid surfaces, is dependent on the presence of retractile type IV pili and is independent of the presence of a flagellum. Surface translocation via twitching motility is powered by the extension and retraction of type IV pili and can manifest as a complex multicellular collective behavior that mediates the active expansion of colonies cultured on the surface of solidified nutrient media, and of interstitial colonies that are cultured at the interface between solidified nutrient media and an abiotic material such as the base of a petri dish or a glass coverslip. Here we describe two methods for assaying twitching motility mediated interstitial colony expansion in P. aeruginosa. The first method, the “Macroscopic Twitching Assay,” can be used to determine if a strain is capable of twitching motility mediated interstitial colony expansion and can also be used to quantitatively assess the influence of mutation or environmental signals on this process. The second method, the “Microscopic Twitching Assay,” can be used for detailed interrogation of the movements of individual cells or small groups of bacteria during twitching motility mediated colony expansion.
Turnbull, L, Strauss, MP, Liew, ATF, Monahan, LG, Whitchurch, CB & Harry, EJ 2014, 'Super-resolution Imaging of the Cytokinetic Z Ring in Live Bacteria Using Fast 3D-Structured Illumination Microscopy (f3D-SIM)', JOVE-JOURNAL OF VISUALIZED EXPERIMENTS, no. 91.View/Download from: Publisher's site
Lazenby, JJ, Griffin, P, Kyd, J, Whitchurch, CB & Cooley, M 2013, 'A Quadruple Knockout Of LasIR And RhlIR Of Pseudomonas Aeruginosa PAO1 That Retains Wild-type Twitching Motility Has Equivalent Infectivity And Persistence To PAO1 In A Mouse Model Of Lung Infection', Plos One, vol. 8, no. 4, pp. 1-10.View/Download from: Publisher's site
It has been widely reported that quorum-sensing incapable strains of Pseudomonas aeruginosa are less virulent than wild type strains. However, quorum sensing mutants of P. aeruginosa have been shown to develop other spontaneous mutations under prolonged culture conditions, and one of the phenotypes of P. aeruginosa that is frequently affected by this phenomenon is type IV pili-dependent motility, referred to as twitching motility. As twitching motility has been reported to be important for adhesion and colonisation, we aimed to generate a quorum-sensing knockout for which the heritage was recorded and the virulence factor production in areas unrelated to quorum sensing was known to be intact. We created a lasIRrhlIR quadruple knockout in PAO1 using a published technique that allows for the deletion of antibiotic resistance cartridges following mutagenesis, to create an unmarked QS knockout of PAO1, thereby avoiding the need for use of antibiotics in culturing, which can have subtle effects on bacterial phenotype. We phenotyped this mutant demonstrating that it produced reduced levels of protease and elastase, barely detectable levels of pyoverdin and undetectable levels of the quorum sensing signal molecules N-3-oxododecanoly-L-homoserine lactone and N-butyryl homoserine lactone, but retained full twitching motility. We then used a mouse model of acute lung infection with P. aeruginosa to demonstrate that the lasIRrhlIR knockout strain showed equal persistence to wild type parental PAO1, induced equal or greater neutrophil infiltration to the lungs, and induced similar levels of expression of inflammatory cytokines in the lungs and similar antibody responses, both in terms of magnitude and isotype. Our results suggest, in contrast to previous reports, that lack of quorum sensing alone does not significantly affect the immunogenicity, infectiveness and persistence of P. aeruginosa in a mouse model of acute lung infection
Gloeckl, S, Ong, V, Patel, P, Tyndall, J, Timms, P, Beagley, K, Allan, J, Armitage, C, Turnbull, L, Whitchurch, CB, Merdanovic, M, Ehrmann, M, Powers, J, Oleksyszyn, J, Verdoes, M, Bogyo, M & Huston, W 2013, 'Identification Of A Serine Protease Inhibitor Which Causes Inclusion Vacuole Reduction And Is Lethal To Chlamydia Trachomatis', Molecular Microbiology, vol. 89, no. 4, pp. 676-689.View/Download from: Publisher's site
The mechanistic details of the pathogenesis of Chlamydia, an obligate intracellular pathogen of global importance, have eluded scientists due to the scarcity of traditional molecular genetic tools to investigate this organism. Here we report a chemical b
Dahan-pasternak, N, Nasereddin, A, Kolevzon, N, Pe'er, M, Wong, W, Shinder, V, Turnbull, L, Whitchurch, CB, Elbaum, M, Gilberger, T, Yavin, E, Baum, J & Dzikowski, R 2013, 'Pfsec13 Is An Unusual Chromatin-associated Nucleoporin Of Plasmodium Falciparum That Is Essential For Parasite Proliferation In Human Erythrocytes', Journal of Cell Science, vol. 126, no. 14, pp. 3055-3069.View/Download from: Publisher's site
In Plasmodium falciparum, the deadliest form of human malaria, the nuclear periphery has drawn much attention due to its role as a sub-nuclear compartment involved in virulence gene expression. Recent data have implicated components of the nuclear envelo
Gloag, ES, Javed, MA, Wang, H, Gee, ML, Wade, SA, Turnbull, L & Whitchurch, CB 2013, 'Stigmergy: A key driver of self-organization in bacterial biofilms.', Communicative and Integrative Biology, vol. 6, no. 6, pp. e27331-e27331.View/Download from: Publisher's site
Bacterial biofilms are complex multicellular communities that are often associated with the emergence of large-scale patterns across the biofilm. How bacteria self-organize to form these structured communities is an area of active research. We have recently determined that the emergence of an intricate network of trails that forms during the twitching motility mediated expansion of Pseudomonas aeruginosa biofilms is attributed to an interconnected furrow system that is forged in the solidified nutrient media by aggregates of cells as they migrate across the media surface. This network acts as a means for self-organization of collective behavior during biofilm expansion as the cells following these vanguard aggregates were preferentially confined within the furrow network resulting in the formation of an intricate network of trails of cells. Here we further explore the process by which the intricate network of trails emerges. We have determined that the formation of the intricate network of furrows is associated with significant remodeling of the sub-stratum underlying the biofilm. The concept of stigmergy has been used to describe a variety of self-organization processes observed in higher organisms and abiotic systems that involve indirect communication via persistent cues in the environment left by individuals that influence the behavior of other individuals of the group at a later point in time. We propose that the concept of stigmergy can also be applied to describe self-organization of bacterial biofilms and can be included in the repertoire of systems used by bacteria to coordinate complex multicellular behaviors.
Horsington, J, Lynn, H, Turnbull, L, Cheng, D, Braet, F, Diefenbach, RJ, Whitchurch, CB, Karupiah, G & Newsome, TP 2013, 'A36-dependent actin filament nucleation promotes release of vaccinia virus', Plos Pathogens, vol. 9, no. 3, pp. e1003239-e1003239.View/Download from: Publisher's site
Cell-to-cell transmission of vaccinia virus can be mediated by enveloped virions that remain attached to the outer surface of the cell or those released into the medium. During egress, the outer membrane of the double-enveloped virus fuses with the plasma membrane leaving extracellular virus attached to the cell surface via viral envelope proteins. Here we report that F-actin nucleation by the viral protein A36 promotes the disengagement of virus attachment and release of enveloped virus. Cells infected with the A36YdF virus, which has mutations at two critical tyrosine residues abrogating localised actin nucleation, displayed a 10-fold reduction in virus release. We examined A36YdF infected cells by transmission electron microscopy and observed that during release, virus appeared trapped in small invaginations at the plasma membrane. To further characterise the mechanism by which actin nucleation drives the dissociation of enveloped virus from the cell surface, we examined recombinant viruses by super-resolution microscopy. Fluorescently-tagged A36 was visualised at sub-viral resolution to image cell-virus attachment in mutant and parental backgrounds. We confirmed that A36YdF extracellular virus remained closely associated to the plasma membrane in small membrane pits.
Hu, H, Harmer, C, Anuj, S, Wainwright, CE, Manos, J, Cheney, J, Harbour, C, Zablotska, I, Turnbull, L, Whitchurch, CB, Grimwood, K, Rose, B & ACFBAL study investigator, T 2013, 'Type 3 secretion system effector genotype and secretion phenotype of longitudinally collected Pseudomonas aeruginosa isolates from young children diagnosed with cystic fibrosis following newborn screening', Clinical Microbiology and Infection, vol. 19, pp. 266-272.View/Download from: Publisher's site
Studies of the type 3 secretion system (T3SS) in Pseudomonas aeruginosa isolates from chronically infected older children and adults with cystic fibrosis (CF) show a predominantly exoS+/exoU) (exoS+) genotype and loss of T3SS effector secretion over time. Relatively little is known about the role of the T3SS in the pathogenesis of early P. aeruginosa infection in the CF airway. In this longitudinal study, 168 P. aeruginosa isolates from 58 children diagnosed with CF following newborn screening and 47 isolates from homes of families with or without children with CF were genotyped by pulsed-field gel electrophoresis (PFGE) and T3SS genotype and phenotype determined using multiplex PCR and western blotting. Associations were sought between T3SS data and clinical variables and comparisons made between T3SS data of clinical and environmental PFGE genotypes. Seventy-seven of the 92 clinical strains were exoS+ (71% secretors (ExoS+)) and 15 were exoU+ (93% secretors (ExoU+)). Initial exoS+ strains were five times more likely to secrete ExoS than subsequent exoS+ strains at first isolation. The proportion of ExoS+ strains declined with increasing age at acquisition. No associations were found between T3SS characteristics and gender, site of isolation, exacerbation, a persistent strain or pulmonary outcomes. Fourteen of the 23 environmental strains were exoS+ (79% ExoS+) and nine were exoU+ (33% ExoU+). The exoU+ environmental strains were significantly less likely to secrete ExoU than clinical strains. This study provides new insight into the T3SS characteristics of P. aeruginosa isolated from the CF airway early in life.
Lek, A, Evesson, FJ, Lemckert, FA, Redpath, G, Turnbull, L, Whitchurch, CB, North, KN, Cooper, ST & Lueders, AK 2013, 'Calpains, Cleaved Mini-Dysferlin(C72), and L-Type Channels Underpin Calcium-Dependent Muscle Membrane Repair', Journal of Neuroscience, vol. 33, no. 12, pp. 5085-5094.View/Download from: Publisher's site
Dysferlin is proposed as a key mediator of calcium-dependent muscle membrane repair, although its precise role has remained elusive. Dysferlin interacts with a new membrane repair protein, mitsugumin 53 (MG53), an E3 ubiquitin ligase that shows rapid recruitment to injury sites. Using a novel ballistics assay in primary human myotubes, we show it is not full-length dysferlin recruited to sites of membrane injury but an injury-specific calpain-cleavage product, mini-dysferlin(C72). Mini-dysferlin(C72)-rich vesicles are rapidly recruited to injury sites and fuse with plasma membrane compartments decorated by MG53 in a process coordinated by L-type calcium channels. Collective interplay between activated calpains, dysferlin, and L-type channels explains how muscle cells sense a membrane injury and mount a specialized response in the unique local environment of a membrane injury. Mini-dysferlin(C72) and MG53 form an intricate lattice that intensely labels exposed phospholipids of injury sites, then infiltrates and stabilizes the membrane lesion during repair. Our results extend functional parallels between ferlins and synaptotagmins. Whereas otoferlin exists as long and short splice isoforms, dysferlin is subject to enzymatic cleavage releasing a synaptotagmin-like fragment with a specialized protein-or phospholipid-binding role for muscle membrane repair.
Lu, J, Carter, DA, Turnbull, L, Rosendale, D, Hedderley, D, Stephens, J, Gannabathula, S, Steinhorn, G, Schlothauer, RC, Whitchurch, CB & Harry, L 2013, 'The effect of New Zealand kanuka, manuka and clover honeys on bacterial growth dynamics and cellular morphology varies according to the species', PLoS One, vol. 8, no. 2, pp. e55898-e55898.View/Download from: Publisher's site
Treatment of chronic wounds is becoming increasingly difficult due to antibiotic resistance. Complex natural products with antimicrobial activity, such as honey, are now under the spotlight as alternative treatments to antibiotics. Several studies have shown honey to have broad-spectrum antibacterial activity at concentrations present in honey dressings, and resistance to honey has not been attainable in the laboratory. However not all honeys are the same and few studies have used honey that is well defined both in geographic and chemical terms. Here we have used a range of concentrations of clover honey and a suite of manuka and kanuka honeys from known geographical locations, and for which the floral source and concentration of methylglyoxal and hydrogen peroxide potential were defined, to determine their effect on growth and cellular morphology of four bacteria: Bacillus subtilis, Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa. While the general trend in effectiveness of growth inhibition was manuka.manuka-kanuka blend.kanuka.clover, the honeys had varying and diverse effects on the growth and cellular morphology of each bacterium, and each organism had a unique response profile to these honeys. P. aeruginosa showed a markedly different pattern of growth inhibition to the other three organisms when treated with sub-inhibitory concentrations of honey, being equally sensitive to all honeys, including clover, and the least sensitive to honey overall. While hydrogen peroxide potential contributed to the antibacterial activity of the manuka and kanuka honeys, it was never essential for complete growth inhibition. Cell morphology analysis also showed a varied and diverse set of responses to the honeys that included cell length changes, cell lysis, and alterations to DNA appearance. These changes are likely to reflect the different regulatory circuits of the organisms that are activated by the stress of honey treatment.
Manos, J, Hu, H, Rose, BR, Wainwright, CE, Zablotska, I, Cheney, J, Turnbull, L, Whitchurch, CB, Grimwood, K, Harmer, C, Anuj, S, Harbour, C & ACFBAL study investigator, T 2013, 'Virulence factor expression patterns in Pseudomonas aeruginosa strains from infants with cystic fibrosis', European Journal of Clinical Microbiology & Infectious Diseases, vol. 32, no. 12, pp. 1583-1592.View/Download from: Publisher's site
Pseudomonas aeruginosa is the leading cause of morbidity and mortality in cystic fibrosis (CF). This study examines the role of organism-specific factors in the pathogenesis of very early P. aeruginosa infection in the CF airway. A total of 168 longitudinally collected P. aeruginosa isolates from children diagnosed with CF following newborn screening were genotyped by pulsed-field gel electrophoresis (PFGE) and phenotyped for 13 virulence factors. Ninety-two strains were identified. Associations between virulence factors and gender, exacerbation, persistence, timing of infection and infection site were assessed using multivariate regression analysis. Persistent strains showed significantly lower pyoverdine, rhamnolipid, haemolysin, total protease, and swimming and twitching motility than strains eradicated by aggressive antibiotic treatments. Initial strains had higher levels of virulence factors, and significantly higher phospholipase C, than subsequent genotypically different strains at initial isolation. Strains from males had significantly lower pyoverdine and swimming motility than females. Colony size was significantly smaller in strains isolated during exacerbation than those isolated during non-exacerbation periods. All virulence factors were higher and swimming motility significantly higher in strains from bronchoalveolar lavage (BAL) and oropharyngeal sites than BAL alone. Using unadjusted regression modelling, age at initial infection and age at isolation of a strain showed U-shaped profiles for most virulence factors. Among subsequent strains, longer time since initial infection meant lower levels of most virulence factors. This study provides new insight into virulence factors underpinning impaired airway clearance seen in CF infants, despite aggressive antibiotic therapy. This information will be important in the development of new strategies to reduce the impact of P. aeruginosa in CF
Muller, P, Alber, DG, Turnbull, L, Schlothauer, RC, Carter, DA, Whitchurch, CB & Harry, L 2013, 'Synergism between medihoney and rifampicin against methicillin-resistant Staphylococcus aureus (MRSA)', PLoS One, vol. 8, no. 2, pp. e57679-e57679.View/Download from: Publisher's site
Skin and chronic wound infections caused by highly antibiotic resistant bacteria such as methicillin-resistant Staphylococcus aureus (MRSA) are an increasing and urgent health problem worldwide, particularly with sharp increases in obesity and diabetes. New Zealand manuka honey has potent broad-spectrum antimicrobial activity, has been shown to inhibit the growth of MRSA strains, and bacteria resistant to this honey have not been obtainable in the laboratory. Combinational treatment of chronic wounds with manuka honey and common antibiotics may offer a wide range of advantages including synergistic enhancement of the antibacterial activity, reduction of the effective dose of the antibiotic, and reduction of the risk of antibiotic resistance. The aim of this study was to investigate the effect of Medihoney in combination with the widely used antibiotic rifampicin on S. aureus. Using checkerboard microdilution assays, time-kill curve experiments and agar diffusion assays, we show a synergism between Medihoney and rifampicin against MRSA and clinical isolates of S. aureus. Furthermore, the Medihoney/rifampicin combination stopped the appearance of rifampicin-resistant S. aureus in vitro. Methylglyoxal (MGO), believed to be the major antibacterial compound in manuka honey, did not act synergistically with rifampicin and is therefore not the sole factor responsible for the synergistic effect of manuka honey with rifampicin. Our findings support the idea that a combination of honey and antibiotics may be an effective new antimicrobial therapy for chronic wound infections.
Ramsey, D, Islam, M, Turnbull, L, Davis, R, Whitchurch, CB & Mcalpine, S 2013, 'Psammaplysin F: A Unique Inhibitor Of Bacterial Chromosomal Partitioning', Bioorganic & Medicinal Chemistry Letters, vol. 23, no. 17, pp. 4862-4866.View/Download from: Publisher's site
Described is the antibiotic activity of a marine natural product. Psammaplysin F (1) inhibited the growth of four Gram-positive strains by >80% at 50 o(sic)M, and the amine at position C-20 is responsible for the observed antibacterial activity. When tes
Riglar, DT, Rogers, KL, Hanssen, E, Turnbull, L, Bullen, HE, Charnaud, SC, Przyborski, J, Gilson, PR, Whitchurch, CB, Crabb, BS, Baum, J & Cowman, AF 2013, 'Spatial association with PTEX complexes defines regions for effector export into Plasmodium falciparum-infected erythrocytes', NATURE COMMUNICATIONS, vol. 4.View/Download from: Publisher's site
Hutchinson, AT, Malik, A, Berkahn, MB, Agostino, M, To, J, Tacchi, JL, Djordjevic, SP, Turnbull, L, Whitchurch, CB, Edmundson, AB, Jones, PM, Raison, RL & Ramsland, PA 2013, 'Formation of Assemblies on Cell Membranes by Secreted Proteins: Molecular Studies of Free Lambda Light Chain Aggregates Found on the Surface of Myeloma Cells.', Biochemical Journal, vol. 454, no. 3, pp. 479-489.View/Download from: Publisher's site
We have described the presence of cell membrane-associated ? free immunoglobulin light chains (FLC) on the surface of myeloma cells. Notably, the anti-?FLC mAb, MDX-1097, is being assessed in clinical trials as a therapy for ? light chain isotype multiple myeloma. Despite the clinical potential of anti-FLC mAbs, there have been limited studies on characterizing membrane-associated FLCs at a molecular level. Furthermore, it is not known if ?FLCs can associate with cell membranes of myeloma cells. In this study, we describe the presence of ?FLCs on the surface of myeloma cells. We found that cell surface-associated ?FLC are bound directly to the membrane and in an aggregated form. Subsequently, membrane interaction studies revealed that ?FLCs interact with saturated zwitterionic lipids such as phosphatidylcholine and phosphatidylethanolamine, and using automated docking, we characterize a potential recognition site for these lipids. Atomic force microscopy confirmed that membrane-associated ?FLCs are aggregated. Given our findings, we propose a model whereby individual FLCs show modest affinity for zwitterionic lipids, with aggregation stabilizing the interaction due to multivalency. Notably, this is the first study to image FLCs bound to phospholipids and provides important insights into the possible mechanisms of membrane association by this unique myeloma surface antigen.
Robinson, MW, Buchtmann, KA, Jenkins, C, Tacchi, JL, Raymond, BBA, To, J, Chowdhury, PR, Woolley, LK, Labbate, M, Turnbull, L, Whitchurch, CB, Padula, MP & Djordjevic, SP 2013, 'MHJ_0125 is an M42 glutamyl aminopeptidase that moonlights as a multifunctional adhesin on the surface of Mycoplasma hyopneumoniae', OPEN BIOLOGY, vol. 3.View/Download from: Publisher's site
Gloag, ES, Turnbull, L, Huang, A, Vallotton, P, Wang, H, Nolan, LM, Mililli, L, Hunt, C, Lu, J, Osvath, SR, Monahan, LG, Cavaliere, R, Charles, IG, Wand, M, Gee, M, Ranganathan, P & Whitchurch, CB 2013, 'Self-organization of bacterial biofilms is facilitated by extracellular DNA', Proceedings of the National Academy of Sciences of the United States of America, vol. 110, no. 28, pp. 11541-11546.View/Download from: Publisher's site
Twitching motility-mediated biofilm expansion is a complex, multicellular behavior that enables the active colonization of surfaces by many species of bacteria. In this study we have explored the emergence of intricate network patterns of interconnected trails that form in actively expanding biofilms of Pseudomonas aeruginosa. We have used high-resolution, phase-contrast time-lapse microscopy and developed sophisticated computer vision algorithms to track and analyze individual cell movements during expansion of P. aeruginosa biofilms. We have also used atomic force microscopy to examine the topography of the substrate underneath the expanding biofilm. Our analyses reveal that at the leading edge of the biofilm, highly coherent groups of bacteria migrate across the surface of the semisolid media and in doing so create furrows along which following cells preferentially migrate. This leads to the emergence of a network of trails that guide mass transit toward the leading edges of the biofilm. We have also determined that extracellular DNA (eDNA) facilitates efficient traffic flow throughout the furrow network by maintaining coherent cell alignments, thereby avoiding traffic jams and ensuring an efficient supply of cells to the migrating front. Our analyses reveal that eDNA also coordinates the movements of cells in the leading edge vanguard rafts and is required for the assembly of cells into the bulldozer aggregates that forge the interconnecting furrows. Our observations have revealed that large-scale self-organization of cells in actively expanding biofilms of P. aeruginosa occurs through construction of an intricate network of furrows that is facilitated by eDNA
Angrisano, F, Sturm, A, Volz, JC, Delves, MJ, Zuccala, ES, Turnbull, L, Dekiwadia, C, Olshina, MA, Marapana, DS, Wong, W, Mollard, V, Bradin, CH, Tonkin, CJ, Gunning, PW, Ralph, SA, Whitchurch, CB, Sinden, RE, Cowman, A, McFadden, GI & Baum, J 2012, 'Spatial localisation of actin filaments across developmental stages of the malaria parasite', PLoS One, vol. 7, no. 2, p. e32188.View/Download from: Publisher's site
Actin dynamics have been implicated in a variety of developmental processes during the malaria parasite lifecycle. Parasite motility, in particular, is thought to critically depend on an actomyosin motor located in the outer pellicle of the parasite cell. Efforts to understand the diverse roles actin plays have, however, been hampered by an inability to detect microfilaments under native conditions. To visualise the spatial dynamics of actin we generated a parasite-specific actin antibody that shows preferential recognition of filamentous actin and applied this tool to different lifecycle stages (merozoites, sporozoites and ookinetes) of the human and mouse malaria parasite species Plasmodium falciparum and P. berghei along with tachyzoites from the related apicomplexan parasite Toxoplasma gondii. Actin filament distribution was found associated with three core compartments: the nuclear periphery, pellicular membranes of motile or invasive parasite forms and in a ring-like distribution at the tight junction during merozoite invasion of erythrocytes in both human and mouse malaria parasites. Localisation at the nuclear periphery is consistent with an emerging role of actin in facilitating parasite gene regulation. During invasion, we show that the actin ring at the parasite-host cell tight junction is dependent on dynamic filament turnover. Super-resolution imaging places this ring posterior to, and not concentric with, the junction marker rhoptry neck protein 4. This implies motor force relies on the engagement of dynamic microfilaments at zones of traction, though not necessarily directly through receptor-ligand interactions at sites of adhesion during invasion. Combined, these observations extend current understanding of the diverse roles actin plays in malaria parasite development and apicomplexan cell motility, in particular refining understanding on the linkage of the internal parasite gliding motor with the extra-cellular milieu.
Baldi, DL, Higginson, E, Hocking, D, Praszkier, J, Cavaliere, R, James, CE, Bennett-wood, V, Azzopardi, K, Turnbull, L, Lithgow, T, Robins-Browne, R, Whitchurch, CB & Tauschek, M 2012, 'The Type Ii Secretion System And Its Ubiquitous Lipoprotein Substrate, Ssle, Are Required For Biofilm Formation And Virulence Of Enteropathogenic Escherichia Coli', Infection And Immunity, vol. 80, no. 6, pp. 2042-2052.View/Download from: Publisher's site
Enteropathogenic Escherichia coli (EPEC) is a major cause of diarrhea in infants in developing countries. We have identified a functional type II secretion system (T2SS) in EPEC that is homologous to the pathway responsible for the secretion of heat-labi
Dearnley, MK, Yeoman, JA, Hanssen, E, Kenny, S, Turnbull, L, Whitchurch, CB, Tilley, L & Dixon, M 2012, 'Origin, composition, organization and function of the inner membrane complex of Plasmodium falciparum gametocytes', Journal of Cell Science, vol. 125, no. 8, pp. 2053-2063.View/Download from: Publisher's site
The most virulent of the human malaria parasites, Plasmodium falciparum, undergoes a remarkable morphological transformation as it prepares itself for sexual reproduction and transmission via mosquitoes. Indeed P. falciparum is named for the unique falci
Green, LC, Kalitsis, P, Chang, TM, Cipetic, M, Kim, JK, Marshall, O, Turnbull, L, Whitchurch, CB, Vagnarelli, P, Samejima, K, Earnshaw, WC, Choo, K & Hudson, D 2012, 'Contrasting Roles Of Condensin I And Condensin Ii In Mitotic Chromosome Formation', Journal of Cell Science, vol. 125, no. 6, pp. 1591-1604.View/Download from: Publisher's site
In vertebrates, two condensin complexes exist, condensin I and condensin II, which have differing but unresolved roles in organizing mitotic chromosomes. To dissect accurately the role of each complex in mitosis, we have made and studied the first verteb
Horsington, J, Turnbull, L, Whitchurch, CB & Newsome, TP 2012, 'Sub-viral imaging of vaccinia virus using super-resolution microscopy', Journal of Virological Methods, vol. 186, pp. 132-136.View/Download from: Publisher's site
The study of host-pathogen interactions over past decades has benefited from advances in microscopy and fluorescent imaging techniques. A particularly powerful model in this field is vaccinia virus (VACV), which due to its amenability to genetic manipulation has been a productive model in advancing the understanding of the transport of subcellular cargoes. Conventional light microscopy imposes an upper limit of resolution of similar to 250 nm, hence knowledge of events occurring at the sub-viral resolution is based predominantly on studies utilising electron microscopy. The development of super-resolution light microscopy presents the opportunity to bridge the gap between these two technologies. This report describes the analysis of VACV replication using fluorescent recombinant viruses, achieving sub-viral resolution with three-dimensional structured illumination microscopy. This is the first report of successfully resolving poxvirus particle morphologies at the scale of single virus particles using light microscopy.
Loo, CY, Lee, WH, Cavaliere, R, Whitchurch, CB, Rohanizadeh, R & Young, PM 2012, 'Superhydrophobic, Nanotextured Polyvinyl Chloride Films For Delaying Pseudomonas Aeruginosa Attachment To Intubation Tubes And Medical Plastics', Acta Biomaterialia, vol. 8, no. 5, pp. 1881-1890.View/Download from: Publisher's site
Bacterial attachment onto the surface of polymers in medical devices such as polyvinyl chloride (PVC) is influenced by the physicochemical properties of the polymer, including its surface hydrophobicity and roughness. In this study, to prevent biofilm fo
Nolan, LM, Croft, L, Jones, PM, George, AM, Turnbull, L, Whitchurch, CB, Beatson, SA & Mattick, JS 2012, 'Extragenic suppressor mutations that restore twitching motility to fimL mutants of Pseudomonas aeruginosa are associated with elevated intracellular cyclic AMP levels', Microbiology Open, vol. 1, no. 4, pp. 490-501.View/Download from: Publisher's site
Cyclic AMP (cAMP) is a signaling molecule that is involved in the regulation of multiple virulence systems of the opportunistic pathogen Pseudomonas aeruginosa. The intracellular concentration of cAMP in P. aeruginosa cells is tightly controlled at the levels of cAMP synthesis and degradation through regulation of the activity and/or expression of the adenylate cyclases CyaA and CyaB or the cAMP phosphodiesterase CpdA. Interestingly, mutants of fimL, which usually demonstrate defective twitching motility, frequently revert to a wild-type twitching-motility phenotype presumably via the acquisition of an extragenic suppressor mutation(s). In this study, we have characterized five independent fimL twitching-motility revertants and have determined that all have increased intracellular cAMP levels compared with the parent fimL mutant. Whole-genome sequencing revealed that only one of these fimL revertants has acquired a loss-of-function mutation in cpdA that accounts for the elevated levels of intracellular cAMP. As mutation of cpdA did not account for the restoration of twitching motility observed in the other four fimL revertants, these observations suggest that there is at least another, as yet unidentified, site of extragenic suppressor mutation that can cause phenotypic reversion in fimL mutants and modulation of intracellular cAMP levels of P. aeruginosa.
Robinson, MW, Alvarado, R, To, J, Hutchinson, AT, Dowdell, SN, Lund, ME, Turnbull, L, Whitchurch, CB, O'Brien, B, Dalton, JP & Donnelly, SM 2012, 'A helminth cathelicidin-like protein suppresses antigen processing and presentation in macrophages via inhibition of lysosomal vATPase', Faseb Journal, vol. 26, no. 11, pp. 4614-4627.View/Download from: Publisher's site
We previously reported the identification of a novel family of immunomodulatory proteins, termed helminth defense molecules (HDMs), that are secreted by medically important trematode parasites. Since HDMs share biochemical, structural, and functional characteristics with mammalian cathelicidin-like host defense peptides (HDPs), we proposed that HDMs modulate the immune response via molecular mimicry of host molecules. In the present study, we report the mechanism by which HDMs influence the function of macrophages. We show that the HDM secreted by Fasciola hepatica (FhHDM-1) binds to macrophage plasma membrane lipid rafts via selective interaction with phospholipids and/or cholesterol before being internalized by endocytosis. Following internalization, FhHDM-1 is rapidly processed by lysosomal cathepsin L to release a short C-terminal peptide (containing a conserved amphipathic helix that is a key to HDM function), which then prevents the acidification of the endolysosomal compartments by inhibiting vacuolar ATPase activity. The resulting endolysosomal alkalization impedes macrophage antigen processing and prevents the transport of peptides to the cell surface in conjunction with MHC class II for presentation to CD4(+) T cells. Thus, we have elucidated a novel mechanism by which helminth pathogens alter innate immune cell function to assist their survival in the host.-Robinson, M. W., Alvarado, R., To, J., Hutchinson, A. T., Dowdell, S. N., Lund, M., Turnbull, L., Whitchurch, C. B., O'Brien, B. A., Dalton, J. P., Donnelly, S. A helminth cathelicidin-like protein suppresses antigen processing and presentation in macrophages via inhibition of lysosomal vATPase
Strauss, M, Liew, AT, Turnbull, L, Whitchurch, CB, Monahan, LG & Harry, L 2012, '3D-SIM super resolution microscopy reveals a bead-like arrangement for FtsZ and the division machinery: implications for triggering cytokinesis', Plos Biology, vol. 10, no. 9, p. e1001389.View/Download from: Publisher's site
FtsZ is a tubulin-like GTPase that is the major cytoskeletal protein in bacterial cell division. It polymerizes into a ring, called the Z ring, at the division site and acts as a scaffold to recruit other division proteins to this site as well as providing a contractile force for cytokinesis. To understand how FtsZ performs these functions, the in vivo architecture of the Z ring needs to be established, as well as how this structure constricts to enable cytokinesis. Conventional wide-field fluorescence microscopy depicts the Z ring as a continuous structure of uniform density. Here we use a form of super resolution microscopy, known as 3D-structured illumination microscopy (3D-SIM), to examine the architecture of the Z ring in cells of two Gram-positive organisms that have different cell shapes: the rod-shaped Bacillus subtilis and the coccoid Staphylococcus aureus. We show that in both organisms the Z ring is composed of a heterogeneous distribution of FtsZ. In addition, gaps of fluorescence were evident, which suggest that it is a discontinuous structure. Time-lapse studies using an advanced form of fast live 3D-SIM (Blaze) support a model of FtsZ localization within the Z ring that is dynamic and remains distributed in a heterogeneous manner. However, FtsZ dynamics alone do not trigger the constriction of the Z ring to allow cytokinesis. Lastly, we visualize other components of the divisome and show that they also adopt a bead-like localization pattern at the future division site. Our data lead us to propose that FtsZ guides the divisome to adopt a similar localization pattern to ensure Z ring constriction only proceeds following the assembly of a mature divisome.
Zuccala, ES, Gout, AM, Dekiwadia, C, Marapana, DS, Angrisano, F, Turnbull, L, Rogers, KL, Whitchurch, CB, Ralph, SA, Speed, TP & Baum, J 2012, 'Subcompartmentalisation of proteins in the rhoptries correlates with ordered events of erythrocyte invasion by the blood stage malaria parasite', PLoS One, vol. 7, no. 9, p. e46160.View/Download from: Publisher's site
Host cell infection by apicomplexan parasites plays an essential role in lifecycle progression for these obligate intracellular pathogens. For most species, including the etiological agents of malaria and toxoplasmosis, infection requires active host-cell invasion dependent on formation of a tight junction - the organising interface between parasite and host cell during entry. Formation of this structure is not, however, shared across all Apicomplexa or indeed all parasite lifecycle stages. Here, using an in silico integrative genomic search and endogenous gene-tagging strategy, we sought to characterise proteins that function specifically during junction-dependent invasion, a class of proteins we term invasins to distinguish them from adhesins that function in species specific host-cell recognition. High-definition imaging of tagged Plasmodium falciparum invasins localised proteins to multiple cellular compartments of the blood stage merozoite. This includes several that localise to distinct subcompartments within the rhoptries. While originating from the same organelle, however, each has very different dynamics during invasion. Apical Sushi Protein and Rhoptry Neck protein 2 release early, following the junction, whilst a novel rhoptry protein PFF0645c releases only after invasion is complete. This supports the idea that organisation of proteins within a secretory organelle determines the order and destination of protein secretion and provides a localisation-based classification strategy for predicting invasin function during apicomplexan parasite invasion.
Ivanov, IE, Boyd, CD, Newell, PD, Schwartz, ME, Turnbull, L, Johnson, MS, Whitchurch, CB, O'Toole, GA & Camesano, TA 2012, 'Atomic force and super-resolution microscopy support a role for LapA as a cell-surface biofilm adhesin of Pseudomonas fluorescens', Research in Microbiology, vol. 163, no. 9-10, pp. 685-691.View/Download from: Publisher's site
Pseudomonas fluorescence Pf0-1 requires the large repeat protein LapA for stable surface attachment. This study presents direct evidence that LapA is a cell-surface-localized adhesin. Atomic force microscopy (AFM) revealed a significant 2-fold reduction in adhesion force for mutants lacking the LapA protein on the cell surface compared to the wild-type strain. Deletion of lapG, a gene encoding a periplasmic cysteine protease that functions to release LapA from the cell surface, resulted in a 2-fold increase in the force of adhesion. Three-dimensional structured illumination microscopy (3D-SIM) revealed the presence of the LapA protein on the cell surface, consistent with its role as an adhesin. The protein is only visualized in the cytoplasm for a mutant of the ABC transporter responsible for translocating LapA to the cell surface. Together, these data highlight the power of combining the use of AFM and 3D-SIM with genetic studies to demonstrate that LapA, a member of a large group of RTX-like repeat proteins, is a cell-surface adhesin
Naughton, S, Parker, D, Seemann, T, Thomas, T, Turnbull, L, Bye, P, Cordwell, SJ, Whitchurch, CB, Manos, J & Rose, B 2011, 'Pseudomonas aeruginosa AES-1 exhibits increased virulence gene expression during chronic infection of cystic fibrosis lung', PLoS ONE, vol. 6, no. 9, pp. e24526-e24526.View/Download from: Publisher's site
Pseudomonas aeruginosa, the leading cause of morbidity and mortality in people with cystic fibrosis (CF), adapts for survival in the CF lung through both mutation and gene expression changes. Frequent clonal strains such as the Australian Epidemic Strain-1 (AES-1), have increased ability to establish infection in the CF lung and to superimpose and replace infrequent clonal strains. Little is known about the factors underpinning these properties. Analysis has been hampered by lack of expression array templates containing CF-strain specific genes. We sequenced the genome of an acute infection AES-1 isolate from a CF infant (AES-1R) and constructed a non-redundant micro-array (PANarray) comprising AES-1R and seven other sequenced P. aeruginosa genomes. The unclosed AES-1R genome comprised 6.254Mbp and contained 6957 putative genes, including 338 not found in the other seven genomes. The PANarray contained 12,543 gene probe spots; comprising 12,147 P. aeruginosa gene probes, 326 quality-control probes and 70 probes for non-P. aeruginosa genes, including phage and plant genes. We grew AES-1R and its isogenic pair AES-1M, taken from the same patient 10.5 years later and not eradicated in the intervening period, in our validated artificial sputum medium (ASMDM) and used the PANarray to compare gene expression of both in duplicate. 675 genes were differentially expressed between the isogenic pairs, including upregulation of alginate, biofilm, persistence genes and virulence-related genes such as dihydroorotase, uridylate kinase and cardiolipin synthase, in AES-1M. Non-PAO1 genes upregulated in AES-1M included pathogenesis-related (PAGI-5) genes present in strains PACS2 and PA7, and numerous phage genes. Elucidation of these genes' roles could lead to targeted treatment strategies for chronically infected CF patients.
Riglar, DT, Richard, D, Wilson, DW, Martin, B, Dekiwadia, C, Turnbull, L, Angrisano, F, Marapana, DS, Rogers, KL, Whitchurch, CB, Beeson, JG, Cowman, A, Ralph, SA & Baum, J 2011, 'Super-Resolution Dissection of Coordinated Events during Malaria Parasite Invasion of the Human Erythrocyte', Cell Host and Microbe, vol. 9, no. 1, pp. 9-20.View/Download from: Publisher's site
Erythrocyte invasion by the merozoite is an obligatory stage in Plasmodium parasite infection and essential to malaria disease progression. Attempts to study this process have been hindered by the poor invasion synchrony of merozoites from the only in vi
Wilksch, JJ, Yang, J, Clements, A, Gabbe, JL, Short, KR, Cao, H, Cavaliere, R, James, CE, Whitchurch, CB, Schembri, MA, Chuah, MLC, Liang, Z-X, Wijburg, OL, Jenney, AW, Lithgow, T & Strugnell, RA 2011, 'MrkH, a Novel c-di-GMP-Dependent Transcriptional Activator, Controls Klebsiella pneumoniae Biofilm Formation by Regulating Type 3 Fimbriae Expression', PLOS PATHOGENS, vol. 7, no. 8.View/Download from: Publisher's site
Yeoman, JA, Hanssen, E, Maier, AG, Klonis, N, Maco, B, Baum, J, Turnbull, L, Whitchurch, CB, Dixon, M & Tilley, L 2011, 'Tracking glideosome-associated protein 50 reveals the development and organization of the inner membrane complex of Plasmodium falciparum', Eukaryotic Cell, vol. 10, no. 4, pp. 556-564.View/Download from: Publisher's site
The most deadly of the human malaria parasites, Plasmodium falciparum, has different stages specialized for invasion of hepatocytes, erythrocytes, and the mosquito gut wall. In each case, host cell invasion is powered by an actin-myosin motor complex tha
Donnelly, SM, O'Neill, S, Stack, CM, Robinson, MW, Turnbull, L, Whitchurch, CB & Dalton, JP 2010, 'Helminth cysteine proteases inhibit TRIF - dependent activation of macrophages via degradation of TLR3.', Journal Of Biological Chemistry, vol. 285, no. 5, pp. 3383-3392.View/Download from: Publisher's site
Helminth pathogens prepare a Th2 type immunological environment in their hosts to ensure their longevity. They achieve this by secreting molecules that not only actively drive type 2 responses but also suppress type 1 responses. Here, we show that the major cysteine proteases secreted from the helminth pathogens Fasciola hepatica (FheCLl) and Schistosoma mansoni (SmCBI) protect mice from the lethal effects oflipopolysaccharide by preventing the release of inflammatory mediators, nitric oxide, interleukin-6, tumor necrosis factor a, and interleukin- 12, from macro phages. The proteases specifically blocl< the MyDSS-independent TRIF-dependent signaling pathway of Toll-like receptor (TLR)4 and TLR3. Microscopical and flow cytometric studies, however, show that alteration of macrophage function by cysteine protease is not mediated by cleavage of components of the TLR4 complex on the cell surface but occurs by degradation ofTLR3 within the endosome. This is the first study to describe a parasite molecule that degrades this receptor and pinpoints a novel mechanism by which helminth parasites modulate the innate immune responses of their hosts to suppress the development ofThl responses.
Fung, C, Naughton, S, Turnbull, L, Tingpej, P, Rose, B, Arthur, J, Hu, H, Harmer, C, Harbour, C, Hassett, DJ, Whitchurch, CB & Manos, J 2010, 'Gene expression of Pseudomonas aeruginosa in a mucin-containing synthetic growth medium mimicking cystic fibrosis lung sputum', Journal of Medical Microbiology, vol. 59, no. 9, pp. 1089-1100.View/Download from: Publisher's site
Pseudomonas aeruginosa airway infection is the leading cause of morbidity and mortality in cystic fibrosis (CF) patients. Various in vitro models have been developed to study P. aeruginosa pathobiology in the CF lung. In this study we produced a modified artificial-sputum medium (ASMDM) more closely resembling CF sputum than previous models, and extended previous work by using strain PAO1 arrays to examine the global transcription profiles of P. aeruginosa strain UCBPP-PA14 under early exponential-phase and stationary-phase growth. In early exponential phase, 38/39 nutrition-related genes were upregulated in line with data from previous in vitro models using UCBPP-PA14. Additionally, 23 type III secretion system (T3SS) genes, several anaerobic respiration genes and 24 quorum-sensing (QS)-related genes were upregulated in ASMDM, suggesting enhanced virulence factor expression and priming for anaerobic growth and biofilm formation. Under stationary phase growth in ASMDM, macroscopic clumps resembling microcolonies were evident in UCBPP-PA14 and CF strains, and over 40 potentially important genes were differentially expressed relative to stationary-phase growth in Luria broth. Most notably, QS-related and T3SS genes were downregulated in ASMDM, and iron-acquisition and assimilatory nitrate reductase genes were upregulated, simulating the iron-depleted, microaerophilic/anaerobic environment of CF sputum. ASMDM thus appears to be highly suitable for gene expression studies of P. aeruginosa in CF.
Hollands, A, Pence, MA, Timmer, AM, Osvath, SR, Turnbull, L, Whitchurch, CB, Walker, MJ & Nizet, V 2010, 'Genetic switch to hypervirulence impairs colonization phenotypes of the globally disseminated Group A Streptococcus M1T1 clone', Journal of Infectious Diseases, vol. 202, no. 1, pp. 11-19.View/Download from: Publisher's site
Background.The recent resurgence of invasive group A streptococcal disease has been paralleled by the emergence of the M1T1 clone. Recently, invasive disease initiation has been linked to mutations in the covR/S 2-component regulator. We investigated whether a fitness cost is associated with the covS mutation that counterbalances hypervirulence. Methods.Wild-type M1T1 group A Streptococcus and an isogenic covS-mutant strain derived from animal passage were compared for adherence to human laryngeal epithelial cells, human keratinocytes, or fibronectin; biofilm formation; and binding to intact mouse skin. Targeted mutagenesis of capsule expression of both strains was performed for analysis of its unique contribution to the observed phenotypes. Results.The covS-mutant bacteria showed reduced capacity to bind to epithelial cell layers as a consequence of increased capsule expression. The covS-mutant strain also had reduced capacity to bind fibronectin and to form biofilms on plastic and epithelial cell layers. A defect in skin adherence of the covS-mutant strain was demonstrated in a murine model.
Kaparakis, M, Turnbull, L, Carneiro, L, Firth, S, Coleman, HA, Parkington, HC, Le Bourhis, L, Karrar, A, Viala, J, Mak, J, Hutton, ML, Davies, JK, Crack, PJ, Hertzog, PJ, Philpott, DJ, Girardin, SE, Whitchurch, CB & Ferrero, RL 2010, 'Bacterial membrane vesicles deliver peptidoglycan to NOD1 in epithelial cells', Cellular Microbiology, vol. 12, no. 3, pp. 372-385.View/Download from: Publisher's site
Gram-negative bacterial peptidoglycan is specifically recognized by the host intracellular sensor NOD1, resulting in the generation of innate immune responses. Although epithelial cells are normally refractory to external stimulation with peptidoglycan, these cells have been shown to respond in a NOD1-dependent manner to Gram-negative pathogens that can either invade or secrete factors into host cells. In the present work, we report that Gram-negative bacteria can deliver peptidoglycan to cytosolic NOD1 in host cells via a novel mechanism involving outer membrane vesicles (OMVs). We purified OMVs from the Gram-negative mucosal pathogens: Helicobacter pylori, Pseudomonas aeruginosa and Neisseria gonorrhoea and demonstrated that these peptidoglycan containing OMVs upregulated NF-kappaB and NOD1-dependent responses in vitro. These OMVs entered epithelial cells through lipid rafts thereby inducing NOD1-dependent responses in vitro. Moreover, OMVs delivered intragastrically to mice-induced innate and adaptive immune responses via a NOD1-dependent but TLR-independent mechanism. Collectively, our findings identify OMVs as a generalized mechanism whereby Gram-negative bacteria deliver peptidoglycan to cytosolic NOD1. We propose that OMVs released by bacteria in vivo may promote inflammation and pathology in infected hosts.
Williams, HL, Turnbull, L, Thomas, SJ, Murphy, A, Stinear, T, Armstrong, DS & Whitchurch, CB 2010, 'A diagnostic PCR assay for the detection of an Australian epidemic strain of Pseudomonas aeruginosa', Annals of Clinical Microbiology and Antimicrobials, vol. 9, no. 18, pp. 1-8.View/Download from: Publisher's site
Background Chronic lung infection with the bacterium Pseudomonas aeruginosa is one of the hallmarks of cystic fibrosis (CF) and is associated with worsening lung function, increased hospitalisation and reduced life expectancy. A virulent clonal strain of P. aeruginosa (Australian epidemic strain I; AES-I) has been found to be widespread in CF patients in eastern Australia. Methods Suppression subtractive hybridization (SSH) was employed to identify genetic sequences that are present in the AES-I strain but absent from the sequenced reference strain PAO1. We used PCR to evaluate the distribution of several of the AES-I loci amongst a collection of 188 P. aeruginosa isolates which was comprised of 35 AES-I isolates (as determined by PFGE), 78 non-AES-I CF isolates including other epidemic CF strains as well as 69 P. aeruginosa isolates from other clinical and environmental sources. Results We have identified a unique AES-I genetic locus that is present in all 35 AES-I isolates tested and not present in any of the other 153 P. aeruginosa strains examined. We have used this unique AES-I locus to develop a diagnostic PCR and a real-time PCR assay to detect the presence of P. aeruginosa and AES-I in patient sputum samples.
Williams, HL, Turnbull, L, Thomas, SJ, Murphy, A, Stinear, T, Armstrong, DS & Whitchurch, CB 2010, 'A diagnostic PCR assay for the detection of an Australian epidemic strain of Pseudomonas aeruginosa', ANNALS OF CLINICAL MICROBIOLOGY AND ANTIMICROBIALS, vol. 9.View/Download from: Publisher's site
Barken, K, Pamp, S, Yang, L, Gjermansen, M, Bertrand, JJ, Klausen, M, Givskov, M, Whitchurch, CB, Engel, JN & Tolker-Nielsen, T 2008, 'Roles of type IV pili, flagellum-mediated motility and extracellular DNA in the formation of mature multicellular structures in Pseudomonas aeruginosa biofilms', Environmental Microbiology, vol. 10, no. 9, pp. 2331-2343.View/Download from: Publisher's site
When grown as a biofilm in laboratory flow chambers Pseudomonas aeruginosa can develop mushroom-shaped multicellular structures consisting of distinct subpopulations in the cap and stalk portions. We have previously presented evidence that formation of the cap portion of the mushroom-shaped structures in P. aeruginosa biofilms occurs via bacterial migration and depends on type IV pili (Mol Microbiol 50: 61-68). In the present study we examine additional factors involved in the formation of this multicellular substructure. While pilA mutants, lacking type IV pili, are deficient in mushroom cap formation, pilH and chpA mutants, which are inactivated in the type IV pili-linked chemosensory system, showed only minor defects in cap formation. On the contrary, fliM mutants, which are non-flagellated, and cheY mutants, which are inactivated in the flagellum-linked chemotaxis system, were largely deficient in cap formation. Experiments involving DNase treatment of developing biofilms provided evidence that extracellular DNA plays a role in cap formation. Moreover, mutants that are deficient in quorum sensing-controlled DNA release formed microcolonies upon which wild-type bacteria could not form caps. These results constitute evidence that type IV pili, flagellum-mediated motility and quorum sensing-controlled DNA release are involved in the formation of mature multicellular structures in P. aeruginosa biofilms.
Han, X, Kennan, RM, Davies, JK, Reddacliff, LA, Dhungyel, OP, Whittington, RJ, Turnbull, L, Whitchurch, CB & Rood, JI 2008, 'Twitching Motility Is Essential For Virulence In Dichelobacter Nodosus', Journal Of Bacteriology, vol. 190, no. 9, pp. 3323-3335.View/Download from: Publisher's site
Type W fimbriae are essential virulence factors of Dichelobacter nodosus, the principal causative agent of ovine foot rot. The fimA fimbrial subunit gene is required for virulence, but fimA mutants exhibit several phenotypic changes and it is not certain
Whitchurch, CB 2006, 'Complexity in '2-component' signal transduction systems', Microbiology Australia, vol. 27, pp. 128-131.
Whitchurch, CB, Comolli, J, Jakobsen, T, Sargent, JL, Bertrand, JJ, West, J, Klausen, M, Waite, L, Kang, PJ, Tolker-Nielsen, T & Engel, JN 2005, 'Pseudomonas Aeruginosa FimL Regulates Multiple Virulence Functions By Intersecting With Vfr-modulated Pathways', Molecular Microbiology, vol. 55, no. 5, pp. 1357-1378.View/Download from: Publisher's site
Virulence of Pseudomonas aeruginosa involves the co-ordinate expression of a range of factors including type IV pili (tfp), the type III secretion system (TTSS) and quorum sensing. Tfp are required for twitching motility, efficient biofilm formation, and
Ru, K, Yuan, Z & Whitchurch, CB 2004, 'tonB3 Is Required For Normal Twitching Motility And Extracellular Assembly Of Type IV Pili', Journal Of Bacteriology, vol. 186, no. 13, pp. 4387-4389.View/Download from: Publisher's site
Three mutants with Tn5-B21 insertion in tonB3 (PA0406) of Pseudomonas aeruginosa exhibited defective twitching motility and reduced assembly of extracellular pili. These defects could be complemented with wild-type tonB3.
Whitchurch, CB, Leech, AJ, Young, M, Kennedy, D, Sargent, JL, Bertrand, JJ, Semmler, AB, Mellick, AS, Martin, PR, Alm, RA, Hobbs, M, Nguyen, L, Commolli, JC, Engel, JN & Darzins, A 2004, 'Characterization Of A Complex Chemosensory Signal Transduction System Which Controls Twitching Motility In Pseudomonas Aeruginosa', Molecular Microbiology, vol. 52, no. 3, pp. 873-893.View/Download from: Publisher's site
Virulence of the opportunistic pathogen Pseudomonas aeruginosa involves the coordinate expression of a wide range of virulence factors including type IV pili which are required for colonization of host tissues and are associated with a form of surface tr
Nouwens, A, Whitchurch, CB, Walsh, B, Schweizer, HP & Cordwell, SJ 2003, 'Proteome Analysis Of Extracellular Proteins Regulated By The Las And Rhl Quorum Sensing Systems In Pseudomonas Aeruginosa Pao1', Microbiology, vol. 149, pp. 1311-1322.View/Download from: Publisher's site
The las and rhl quorum sensing (QS) systems regulate the expression of several genes in response to cell density changes in Pseudomonas aeruginosa. Many of these genes encode surface-associated or secreted virulence factors. Proteins from stationary phas
Whitchurch, CB 2003, 'FimX, A Multidomain Protein Connecting Environmental Signals To Twitching Motility In Pseudomonas Aeruginosa', Journal Of Bacteriology, vol. 185, no. 24, pp. 7068-7076.View/Download from: Publisher's site
Twitching motility is a form of surface translocation mediated by the extension, tethering, and retraction of type IV pili. Three independent Tn5-B21 mutations of Pseudomonas aeruginosa with reduced twitching motility were identified in a new locus which
Whitchurch, CB & Semmler, AB 2002, 'Quorum Sensing Is Not Required For Twitching Motility In Pseudomonas Aeruginosa', Journal Of Bacteriology, vol. 184, no. 13, pp. 3598-3604.View/Download from: Publisher's site
It has been reported that mutations in the quorum-sensing genes lasI and rhlI in Pseudomonas aeruginosa result in, among many other things, loss of twitching motility (A. Glessner, R. S. Smith, B. H. Iglewski, and J. B. Robinson, J. Bacteriol. 181:1623-1
Whitchurch, CB, Erova, T, Emery, J, Sargent, JL, Harris, JM, Semmler, AB, Young, M & Wozniak, D 2002, 'Phosphorylation Of The Pseudomonas Aeruginosa Response Regulator Algr Is Essential For Type Iv Fimbria-mediated Twitching Motility', Journal Of Bacteriology, vol. 184, no. 16, pp. 4544-4554.View/Download from: Publisher's site
The response regulator AlgR is required for both alginate biosynthesis and type IV fimbria-mediated twitching motility in Pseudomonas aeruginosa. In this study, the roles of AlgR signal transduction and phosphorylation in twitching motility and biofilm f
Whitchurch, CB, Sargent, JL & Levesque, R 2002, 'Differential Regulation Of Twitching Motility And Elastase Production By Vfr In Pseudomonas Aeruginosa', Journal Of Bacteriology, vol. 184, no. 13, pp. 3605-3613.View/Download from: Publisher's site
Vfr, a homolog of Escherichia coli cyclic AMP (cAMP) receptor protein, has been shown to regulate quorum sensing, exotoxin A production, and regA transcription in Pseudomonas aeruginosa. We identified a twitching motility-defective mutant that carries a
Bacterial biofilms are structured communities of cells enclosed in self-produced hydrated polymeric matrix adherent to an inert or living surface (1). Formation of these sessile communities and their inherent resistance to antibiotics and host immune attack are at the root of many persistent and chronic bacterial infections (1), including those caused by Pseudomonas aeruginosa, which has been intensively studied as a model for biofilm formation (2, 3). The matrix, which holds bacterial biofilms together, is a complex mixture of macromolecules including exopolysaccharides, proteins, and DNA (4). The latter has been presumed to be derived from lysed cells and has not been thought to represent an important component of biofilm structure. However, it has been known for many years that some bacteria, including P. aeruginosa, produce substantial quantities of extracellular DNA through a mechanism that is thought to be independent of cellular lysis and that appears to involve the release of small vesicles from the outer membrane
Croft, L, Beatson, SA, Whitchurch, CB, Huang, B, Blakeley, R & Mattick, J 2000, 'An Interactive Web-based Pseudomonas Aeruginosa Genome Database: Discovery Of New Genes, Pathways And Structures', Microbiology-uk, vol. 146, no. 10, pp. 2351-2364.
Semmler, AB, Whitchurch, CB & Leech, AJ 2000, 'Identification Of A Novel Gene, FimV, Involved In Twitching Motility In Pseudomonas Aeruginosa', Microbiology-uk, vol. 146, pp. 1321-1332.
Transposon mutagenesis was used to identify a new locus required for twitching motility in Pseudomonas aeruginosa. Four Tn5-B21 mutants which lacked twitching motility and a fifth which exhibited impaired motility were found to map to the same KpnI restr
Whitchurch, CB & Croft, L 2000, 'A minimal tiling path cosmid library for functional analysis of the Pseudomonas aeruginosa PAO1 genome', Microbial and Comparative Genomics, vol. 5, no. 4, pp. 189-203.
Comolli, J, Hauser, A, Waite, L, Whitchurch, CB & Engel, JN 1999, 'Pseudomonas Aeruginosa Gene Products Pilt And Pilu Are Required For Cytotoxicity In Vitro And Virulence In A Mouse Model Of Acute Pneumonia', Infection And Immunity, vol. 67, no. 7, pp. 3625-3630.
Type TV pill of the opportunistic pathogen Pseudomonas aeruginosa mediate twitching motility and act as receptors for bacteriophage infection. They are also important bacterial adhesins, and nonpiliated mutants of P. aeruginosa have been shown to cause l
Semmler, AB & Whitchurch, CB 1999, 'A Re-examination Of Twitching Motility In Pseudomonas Aeruginosa', Microbiology-uk, vol. 145, no. 1, pp. 2863-2873.
Twitching motility is a form of solid surface translocation which occurs in a wide range of bacteria and which is dependent on the presence of functional type IV fimbriae or pili. A detailed examination of twitching motility in Pseudomonas aeruginosa und
Whitchurch, CB & Alm, RA 1996, 'The Alginate Regulator AlgR And An Associated Sensor FimS Are Required For Twitching Motility In Pseudomonas Aeruginosa', Proceedings Of The National Academy Of Sciences Of The United States Of America, vol. 93, no. 18, pp. 9839-9843.View/Download from: Publisher's site
Mucoid strains of Pseudomonas aeruginosa isolated from the lungs of cystic fibrosis patients produce large amounts of the exopolysaccharide alginate. AlgR has long been considered a key regulator of alginate production, but its cognate sensor has not bee
Type-4 fimbriae (or pill) are filaments found at the poles of a wide range of bacterial pathogens, including Neisseria gonorrhoeae, Moraxella bovis, Dichelobacter nodosus and Pseudomonas aeruginosa. They are composed of a small subunit which is highly co
Whitchurch, CB 1994, 'Characterization Of A Gene, PilU, Required For Twitching Motility But Not Phage Sensitivity In Pseudomonas aeruginosa', Molecular Microbiology, vol. 13, no. 6, pp. 1079-1091.View/Download from: Publisher's site
Type 4 fimbriae (or pili) are associated with a farm of bacterial surface translocation known as twitching motility. Fimbriae are also associated with sensitivity to certain bacteriophages such as PO4. Transposon mutagenesis was used to generate a librar
Whitchurch, CB 1994, 'Escherichia-coli Contains A Set Of Genes Homologous To Those Involved In Protein Secretion, DNA Uptake And The Assembly Of Type-4 Fimbriae In Other Bacteria', Gene, vol. 150, no. 1, pp. 9-15.View/Download from: Publisher's site
A specialised system involved in a diverse array of functions, including the biogenesis of fimbriae, protein secretion and DNA uptake, has recently been found to be widespread in the eubacteria. These systems have in common several sets of related genes,
Whitchurch, CB, Hobbs, M, Livingston, S & Krishnapillai, V 1991, 'Characterization Of A Pseudomonas-aeruginosa Twitching Motility Gene And Evidence For A Specialized Protein Export System Widespread In Eubacteria', Gene, vol. 101, no. 1, pp. 33-44.View/Download from: Publisher's site
Type-4 fimbriae (pili) are associated with a phenomenon known as twitching motility, which appears to be involved with bacterial translocation across solid surfaces. Pseudomonas aeruginosa mutants which produce fimbriae, but which have lost the twitching
Bottomley, AL, Turnbull, L, Whitchurch, CB & Harry, EJ 2017, 'Immobilization Techniques of Bacteria for Live Super-resolution Imaging Using Structured Illumination Microscopy.' in Pontus Nordenfelt and Mattias Collin (ed), Bacterial Pathogenesis, pp. 197-209.View/Download from: Publisher's site
Advancements in optical microscopy technology have allowed huge progression in the ability to understand protein structure and dynamics in live bacterial cells using fluorescence microscopy. Paramount to high-quality microscopy is good sample preparation to avoid bacterial cell movement that can result in motion blur during image acquisition. Here, we describe two techniques of sample preparation that reduce unwanted cell movement and are suitable for application to a number of bacterial species and imaging methods.
Turnbull, L & Whitchurch, CB 2014, 'Motility Assay: Twitching Motility' in Filloux, A & Ramos, JL (eds), Pseudomonas Methods and Protocols, Springer New York, New York, pp. 73-86.View/Download from: Publisher's site
Twitching motility is a mode of solid surface translocation that occurs under humid conditions on semisolid or solid surfaces, is dependent on the presence of retractile type IV pili and is independent of the presence of a flagellum. Surface translocation via twitching motility is powered by the extension and retraction of type IV pili and can manifest as a complex multicellular collective behavior that mediates the active expansion of colonies cultured on the surface of solidified nutrient media, and of interstitial colonies that are cultured at the interface between solidified nutrient media and an abiotic material such as the base of a petri dish or a glass coverslip. Here we describe two methods for assaying twitching motility mediated interstitial colony expansion in P. aeruginosa. The first method, the Macroscopic Twitching Assay, can be used to determine if a strain is capable of twitching motility mediated interstitial colony expansion and can also be used to quantitatively assess the influence of mutation or environmental signals on this process. The second method, the Microscopic Twitching Assay, can be used for detailed interrogation of the movements of individual cells or small groups of bacteria during twitching motility mediated colony expansion.
Watson, L, Connell, J, Harding, A & Whitchurch, CB 2009, 'Toward using an oxidatively damaged plasmid as an intra- and inter-laboratory standard for ancient DNA studies' in Haslam, M, Robertson, G, Crowther, A, Nugent, S & Kirkwood, L (eds), Archaeological Science Under a Microscope: Studies in Residue and ancient DNA Analysis in Honour of Thomas H. Loy, ANU E Press, Canberra, Australia, pp. 141-150.
The following paper was originally presented by Dr Thomas H. Loy at the 6th International Conference on Ancient DNA and Associated Biomolecules held in Israel, July 2002. It is included here with editorial and formatting changes with the intention of demonstrating the passion and lateral thinking that underpinned Tomï½s approach to the field of Molecular Archaeology. The paper represents research from three honours projects conducted during the late 1990s and early 2000s. Building a modern model for ancient DNA that could be used during routine procedures was a concept that Tom had long held as an important step forward for the burgeoning discipline. With the equipment and technology that was available at the time, the Damaged Plasmid Model concept was completely viable and worthy of detailed validation. As with all historical accounts, an understanding of more recent developments in molecular techniques and equipment will highlight the need for considerable optimisation of the model before it can be used as an interlaboratory standard for ancient DNA
Whitchurch, CB 2006, 'Biogenesis and Funciton of Type IV Pili in Pseudomonas Species' in Ramos, JL & Levesque, RC (eds), Pseudomonas Volume 4: Molecular Biology of Emerging Issues, Springer, Netherlands, pp. 139-188.View/Download from: Publisher's site
Type IV pili or fimbriae are non-flagellar, filamentous surface appendages that are associated with a number of biological activities in bacteria. These processes include a form of surface translocation termed twitching motility; bacteriophage sensitivity; attachment to biotic (bacteria, plant, animal) and abiotic surfaces; biofilm development; and the uptake of naked DNA by natural transformation. Many of these biological functions are reliant on the ability of these structures to extend and retract.
Lu, J, Whitchurch, C, Turnbull, L, Carter, D, Schlothauer, R & Harry, L 2012, 'THE THERAPEUTIC USE OF HONEY ON CHRONIC WOUND INFECTIONS', WOUND REPAIR AND REGENERATION, pp. A73-A73.
Mueller, P, Turnbull, L, Schlothauer, R, Whitchurch, C & Harry, E 2012, 'NEW ZEALAND MANUKA HONEY HELPS HUMAN KERATINOCYTES TO SURVIVE IN PRESENCE OF S-AUREUS', WOUND REPAIR AND REGENERATION, WILEY-BLACKWELL, pp. A75-A75.
Tillev, L, McMillan, P, Dixon, M, Hanssen, E, Yeoman, J, Whitchurch, C & Klonis, N 2011, 'Super-resolution optical imaging of malaria parasites', 2011 Int. Quantum Electron. Conf., IQEC 2011 and Conf. Lasers and Electro-Optics, CLEO Pacific Rim 2011 Incorporating the Australasian Conf. Optics, Lasers and Spectroscopy and the Australian Conf., Conference on Lasers and Electro-Optics and Quantum Electronics and Laser Science Conference, IEEE, Sydney, NSW, Australia, pp. 368-369.View/Download from: Publisher's site
3-D Structured illumination microscopy (SIM), a super-resolution optical microscopy technique that allows an 8-fold increase in volume resolution, is providing new views of the cellular substructure of the malaria parasite, Plasmodium falciparum. © 2011 IEEE.
Vallotton, P, Mililli, L, Turnbull, L & Whitchurch, CB 2010, 'Segmentation of Dense 2D Bacilli Populations', 2010 International Conference on Digital Image Computing: Techniques and Applications, International Conference on Digital Image Computing: Techniques and Applications, IEEE xplore, Sydney, pp. 82-86.View/Download from: Publisher's site
Bacteria outnumber all other known organisms by far so there is considerable interest in characterizing them in detail and in measuring their diversity, evolution, and dynamics. Here, we present a system capable of identifying rod-like bacteria (bacilli) correctly in high resolution phase contrast images. We use a probabilistic model together with several purpose-designed image features in order to split bacteria at the septum consistently. Our method commits less than 1% error on test images. Our method should also be applicable to study dense 2D systems composed of elongated elements, such as some viruses, molecules, parasites (plasmodium, euglena), diatoms, and crystals.
Vallotton, P, Sun, C, Wang, D, Ranganathan, P, Turnbull, L & Whitchurch, CB 2009, 'Segmentation and tracking of individual Pseudomonas aeruginosa bacteria in dense populations of motile cells', Proceedings of Image and Vision Computing New Zealand 2009, Image and Vision Computing Conference, IEEE, Wellington, NZ, pp. 221-225.View/Download from: Publisher's site
The dynamics of individual bacteria underlies the manifestation of complex multicellular behaviours such as biofilm development and colony expansion. High resolution movies of expanding bacterial colonies reveal intriguing patterns of cell motions. A quantitative understanding of the observed behaviour in relation to the bacterias own motile apparatus and to hydrodynamic forces requires that bacteria be identified and tracked over time. This represents a demanding undertaking as their size is close to the diffraction limit; they are very close to each other; and a typical image may contain over a thousand cells. Here, we describe the approach that we have developed to segment individual bacteria and track them in high resolution phase contrast microscopy movies. We report that over 99% of nonoverlapping bacteria could be segmented correctly using mathematical morphology, and we present preliminary results that exploit this new capability.
Kaparakis, M, Turnbull, L, Carneiro, L, Firth, S, Coleman, HA, Parkington, HC, Le Bourhis, L, Karrar, A, Viala, J, Mak, J, Hutton, M, Davies, JK, Philpott, D, Girardin, S, Whitchurch, CB & Ferrero, RL 2008, 'Bacterial outer membrane vesicles: A new mechanism for NOD1-dependent responses in epithelial cells', HELICOBACTER, pp. 394-394.