Bacteriology

Event Date: 
Wednesday, April 29, 2015 - 18:00 - 18:15
Institution: 
University of New South Wales (UNSW)
Title: 

Bacterial secondary metabolite prodigiosin inhibit biofilm development by cleaving extracellular DNA

Abstract: 

Prodigiosin a bacterial secondary metabolite is a heterocyclic compound belongs to the class of tripyrrole, synthesized by various strains of bacteria includes Serratia species. Research on prodigiosin is under limelight for past 10 years from clinical and pharmacological aspects in relevance to its potential to be drug for cancer therapy by inducing apoptosis in several cancer cell lines. Reports suggest that prodigiosin promotes oxidative damage to DNA in presence of copper ion and consequently lead to inhibition of cell-cycle progression and inducing cell death. However, prodigiosin has not been previously implicated in biofilm inhibition. We performed experiments to reveal any link between prodigiosin and biofilm inhibition through degradation of extracellular DNA which plays a major role in biofilm establishment. Our study showed that prodigiosin (extracted from Serratia culture) has strong DNA cleaving property but does not intercalate with nitrogenous bases of DNA. Using P. aeruginosa PA14 wild-type strain as a model organism we showed that bacterial cells treated with prodigiosin showed significant reduction in its cells surface hydrophobicity and consequently affecting surface energies and physico-chemical property essential for bacterial adhesion and aggregation. We also found that prodigiosin did not influence planktonic growth of P. aeruginosa however, was successful in inhibiting the establishment of biofilms includes decrease in biofilm thickness, adhesion to substratum, decrease in biovolume, microcolony formation and also significantly dispersed pre-established biofilm of P. aeruginosa. This novel function on the biofilm inhibition of prodigiosin could be used to interfere with risks associated with bacterial biofilms. 

Event Date: 
Wednesday, February 25, 2015 - 17:30 - 18:00
Institution: 
University of Melbourne
Title: 

Genomic epidemiology of antibiotic resistant bacteria

Abstract: 

Microbial populations contribute to human disease in a variety of ways, both as agents of infection and as healthy components of the microbiome. Genomic approaches can offer deep insights into this hidden microbial world, including revealing the composition of microbial communities, tracking the movement of individual organisms, and illuminating evolutionary changes. Here I will present recent work applying genomic epidemiology to investigate the emergence and spread of antibiotic resistance in a range of important pathogens, including typhoid, dysentery and the emerging hospital superbug Klebsiella.

Event Date: 
Wednesday, October 29, 2014 - 18:15 - 18:30
Institution: 
UTS
Title: 

Stigmergic social behaviours facilitate the active expansion of Pseudomonas aeruginosa interstitial biofilms.

Abstract: 

Erin S. Gloag1, Awais Javed2, Huabin Wang3, Michelle L. Gee3, Scott A. Wade2, Lynne Turnbull1, Cynthia B. Whitchurch1*
1 The ithree institute, University of Technology Sydney, Ultimo, NSW, 2007, Australia.
2 Faculty of Engineering and Industrial Sciences, Swinburne University of Technology, Hawthorn, VIC, 3122, Australia
3 School of Chemistry, University of Melbourne, Parkville, VIC, 3010, Australia.
 
Biofilms are often found associated with infections of implantable medical devices; accounting for approximately half of all nosocomial infections. Biofilms are often thought of as sessile surface-attached communities that are embedded in a protective slimy matrix. However, many bacterial pathogens also have the capacity to actively expand their biofilm communities via complex multi-cellular behaviours. We have observed that when P. aeruginosa is cultured at the interstitial surface between a coverslip and solidified nutrient media the resulting biofilm actively expands via twitching motility and is characterised by the formation of an extensive pattern of interconnected trails.
We set out to identify the factors governing pattern formation and coordinated movement during P. aeruginosa interstitial biofilm expansion. Our observations have revealed that during biofilm migration the cells at the advancing edge create furrows as they migrate across the semi-solid media The following cells are preferentially confined to these furrows, resulting in the emergence of an interconnected furrow network and the subsequent extensive large scale-patterning characteristic of these biofilms.
Stigmergy is a concept which describes self-organisation processes observed in higher organisms and abiotic systems through 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. Our observations indicate that self-organised pattern formation in P. aeruginosa interstitial biofilms is also a stigmergic phenomenon. To our knowledge this is the first time that stigmergy has been identified as a mechanism of self-organisation of bacterial biofilms and propose that the concept of stigmergy can be included in the repertoire of systems used by bacteria to co-ordinate complex multicellular behaviours. We are currently exploring the development of novel antimicrobial strategies aimed at controlling and inhibiting biofilm expansion in medical settings via exploiting our new understanding of biofilm expansion.

Event Date: 
Wednesday, September 24, 2014 - 19:15 - 19:45
Institution: 
Australian Centre for Ecogenomics
Title: 

Evolution and function of marsupial gut microbiota

Abstract: 

Despite growing interest in the form and function of mammalian gut microbiomes, few culture-independent studies have focused on the microbiomes of Australian marsupials. In particular, how do the microbiota of the koala and other toxic Eucalypt folivores enable these animals to occupy this specialised dietary niche? We are addressing this question by surveying the gut microbial communities of diprotodont marsupials across a range of phylogeny, diet, and gut morphology. Furthermore, beyond community profiles, we are probing community functionality through metagenome shotgun sequencing of the Vombatiformes (koala and wombat) gut microbiota. Using differential coverage binning and metabolic reconstruction, we have the comparative power to identify specialised pathways in koala and wombat microbiota, from the community-level down to the level of individual population genomes.

Event Date: 
Wednesday, September 24, 2014 - 18:00 - 18:15
Institution: 
University of Sydney
Title: 

Microbiota characterisation in the Tasmanian devil

Abstract: 

The Tasmanian devil (Sarcophilus harrisii), the world’s largest remaining carnivorous marsupial, faces extinction due to the spread of a contagious cancer called Devil Facial Tumour Disease (DFTD). The lack of a description of the bacterial community composition in the species represents a major gap in our knowledge of Tasmanian devil biology. In this study we characterised 12 microbiomes from four body sites, including mouth, gut, skin and pouch, in five Tasmanian devils via PCR amplification of 16S rRNA gene V1-V3 regions followed by 454 sequencing.  A total of 249,224 reads with an average sequence length of 489 bp were obtained after length and quality filtering. The reads further clustered into 14533 operational taxonomic units (OTUs; sequence identity cutoff of >97%) that were classified to 24 phyla spanning 275 families. Higher levels of bacterial species richness were observed in the pouch and skin than in the mouth and gut. The pouch and skin showed similar microflora compositions, which may vary between animals, possibly due to different environments. Distinct from the previously reported koala gut microbiota [1], which is dominated by Bacteroidetes and Firmicutes, the devil gut microbiota was found to be dominated by Fusobacteria, Firmicutes and Proteobacteria, comprising up to 73.7-94.3% of the community. This study has greatly improved our understanding of the microbial communities in the Tasmanian devil, which will significantly contribute to the effort to conserve the species.

Event Date: 
Wednesday, July 30, 2014 - 19:00 - 19:45
Institution: 
UTS
Title: 

The production of public goods in bacterial biofilms

Abstract: 

“Public goods” in bacterial communities are extracellular products that are released by a sub-set of individuals that provide benefits to the local population.  Extracellular DNA (eDNA) is a public good that has been found to be required for the formation of sessile biofilms by many species of bacteria including Pseudomonas aeruginosa.  We have recently shown that eDNA also facilitates the active expansion of P. aeruginosa biofilms by engineering the formation of a network of interconnected furrows and directing traffic flow throughout the furrow network to efficiently supply cells to the leading edge of the expanding biofilm. The mechanism by which eDNA is produced by P. aeruginosa and many other bacterial species is poorly understood. We have discovered a novel mechanism that accounts for the production of eDNA as well as other “public goods” in P. aeruginosa biofilms. 

Event Date: 
Wednesday, June 25, 2014 - 19:00 - 20:00
Institution: 
UTS
Title: 

Honey: Return of an Ancient Remedy

Abstract: 

Chronic wounds are a tremendous burden to human health worldwide, currently affecting 2% of the population in developed countries, with significant social and economic costs. Treatment of these wounds is becoming increasingly difficult due to infections caused by multidrug resistant bacteria. Honey is increasingly being used as a topical treatment for these wounds. New Zealand manuka honey has potent broad-spectrum antimicrobial activity and resistance to honey has not been attainable in the laboratory. Approved medical-grade manuka honey and honey dressings are readily available for use in wound treatment but their use is limited, largely due to lack of information about how they work. This talk will provide an overview of where we are at with research examining the value of honey as an antibacterial agent in wound treatment. It will include how different bacteria respond to honey, synergistic interaction studies using manuka honey and antibiotics currently used to treat infected wounds, and biofilm prevention and eradication studies.

Event Date: 
Wednesday, June 25, 2014 - 18:00 - 18:15
Institution: 
UNSW
Title: 

Nitric oxide treatment for the control of reverse osmosis membrane biofouling

Abstract: 

Biofouling remains a key challenge for membrane based water treatment systems.  This study investigated the dispersal potential of the nitric oxide (NO) donor compound, PROLI NONOate, on single species biofilms formed by bacteria isolated from industrial membrane bioreactor and reverse osmosis (RO) membranes, as well as on mixed species biofilms.  The potential of PROLI NONOate to control RO membrane biofouling was also examined.  Confocal microscopy revealed that different bacteria responded differently to PROLI NONOate exposure.  However, the addition of NO induced dispersal in all but two of the bacteria tested and successfully reduced mixed species biofilms.  The addition of 40 µM PROLI NONOate at 24 h intervals to a laboratory-scale RO system led to a 92% reduction in the rate of biofouling (pressure rise over a given period) by a bacterial community cultured from an industrial RO membrane.  Confocal microscopy and EPS extraction revealed that PROLI NONOate treatment led to a 48% reduction in polysaccharides, a 66% reduction in proteins and a 29% reduction in microbial cells compared to the untreated control.  A reduction in biofilm surface coverage (59% vs. 98%, treated vs. control) and average thickness (20 µm vs. 26 µm, treated vs. control) was also observed.  The addition of PROLI NONOate led to a 22% increase in the time required for the RO module to reach its maximum TMP, further indicating that NO treatment delayed fouling.  Pyrosequencing analysis revealed that the NO treatment did not significantly alter the microbial community composition of the membrane biofilm.  These results present strong evidence for the application of PROLI NONOate for prevention of RO biofouling in an industrial setting.

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