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Event Date: 
Wednesday, July 30, 2014 - 18:00 - 18:15
Institution: 
UTS
Title: 

Exploring coral-bacteria interactions: where are they, how do they get there and what do they do?

Abstract: 

Microorganisms live in tight ecological associations with corals, but microbial community composition, functions and behaviours within coral reef ecosystems are not yet fully understood. To examine the community structure, metabolic capacity and the potential role of chemotaxis in the ecology of coral reef bacterial communities, we performed a suite of laboratory, in-situ and thermal stress experiments on Heron Island, the Great Barrier Reef (GBR). To characterise patterns in microbial composition and metabolic capacity across different niches on a coral reef, metagenomes were sequenced from seawater samples associated with the surfaces of corals, the sandy substrate and in open water, outside of the reef. Within these environments we also examined the potential ecological role of chemotaxis among coral associated bacteria, by using laboratory and in situ chemotaxis assays to test for levels of chemotaxis towards several chemoattractants known to be released by corals and their symbiotic dinoflagelletes including amino acids, carbohydrates, ammonium chloride, and dimethylsulfonopropionate (DMSP). Finally, to determine how environmental variability, specifically thermal stress, influences bacterial community composition, behaviour and metabolic capacity, manipulation experiments were conducted using Pocillopora damicornis in flow-through aquatic systems on Heron Island.
 We found that the composition and metabolic potential of coral reef bacteria is highly heterogeneous across a coral reef ecosystem, with a shift from an oligotroph-dominated community (e.g. SAR11, Prochlorococcus, Synechococcus) in the open water and sandy substrate niches, to a community characterised by an increased frequency of copiotrophic bacteria (e.g. Vibrio, Pseudoalteromonas, Alteromonas) in the coral seawater niches. Among the major functional patterns observed were significant increases in genes associated with bacterial motility and chemotaxis in samples associated with the surfaces of coral colonies. These patterns were directly confirmed by chemotaxis experiments, which demonstrated that bacteria associated with the surfaces of the corals exhibited high levels of chemotaxis, particularly towards DMSP and several amino acids. Levels of chemotaxis by coral-associated bacteria were consistently higher than those demonstrated by non-coral associated bacteria. The phylogenetic composition of the chemotactic microbes, determined using 16S rRNA amplicon pyrosequencing, differed to the background community in the surrounding seawater, and incorporated several known coral-associated bacteria, Rhodobacteraceae, Flavobacteriaceae, Pseudomonadaceae and included potentially pathogenic Vibrios. Notably many of these bacteria, specifically Rhodobacterales, Flavobacterales and Vibrionales also became the dominant coral associated organisms under conditions of thermal stress experiments, indicating that these copiotrophic and chemotactic bacteria become key colonisers of thermally stressed corals.
Taken together our data demonstrate that coral reef bacterial communities are highly dynamic and that key groups of copiotrophic bacteria have the capacity to use sensitive chemotaxis to exploit nutrient gradients and potentially locate their coral hosts. Under conditions of heat stress, these behaviours may allow pathogenic organisms to locate and infect compromised hosts. 

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. 

It was nice to see the JAMS crowd infultrating the ASM conference in Melbourne. As people prepare to migrate north for ISME in Korea don't forget to come into the Australian Museum for a taste of local microbiology offerings.

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 - 18:15 - 18:30
Institution: 
CSIRO
Title: 

Biomes of Australian Soil Environments (BASE)

Abstract: 

The Biomes of Australian Soil Environments (BASE) is a soil microbial diversity database faciliatated by Bioplatforms Australia and currently involving 14 Australian agencies. The BASE project is collecting biodiversity data from Australian soils in the form of amplicon sequences and amplication free metagenomic sequences. Sequence data is accompanied by rich contextual data describing soil physical and chemical attributes, land use, overlying vegetation and climate. All information collected is made publicly available via the BASE database. Thus far BASE has collected approximately 900 samples, with data from over 400 of these being currently available. I will briefly introduce the BASE project and its newly deployed database by describing the sampling and sequencing protocols and demonstrating the databases search capabilities.

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.

Event Date: 
Wednesday, May 28, 2014 - 18:15 - 18:30
Institution: 
CSIRO
Title: 

Cairneyella

Abstract: 

In September 1999, I collected a small heath plant from a large sandstone outcrop near the Murphy’s Glen campsite in the Blue Mountains west of Sydney. This seedling had been growing in just a few centimetres of sand atop the rock. The shallowness of soil meant its root system was perpendicular to the stem, and spread out like a spider’s web from the base. Heath plants have unusual roots; they’re very fine, being only marginally thicker than a human hair. I took the plant back to the laboratories at University of Western Sydney and carefully cut these hair roots up in small pieces. I surface sterilised the pieces in bleach and placed each piece, numbered and its location in the root system recorded, onto an agar plate. From these tiny root pieces grew a host of very slow growing non-spore producing fungi. Most of these fungi were ericoid mycorrhizal (ERM) fungi – these fungi form a symbiosis with heath plants – facilitating their growth in challenging places such as acid bogs, nutrient poor sands and soils rich in metals such as cadium and zinc. Since 1999, I’ve undertaken quite a bit of work on the most abundant ERM fungus from this one seedling, and with the help of various collaborators we have observed the structures it forms in roots of heath plants, how it enhances the growth of heath seedlings and examined its carbon, nitrogen and phosphorus catabolism. It was, and still is, the most studied Australian ericoid mycorrhizal fungus. 
Upon moving to CSIRO in 2007, I left the last six cultures in the fridge in Dr. Peter McGee’s laboratory and it was here that they remained until 2013 when I retrieved them on Peter’s retirement. Just two of the last six survived the long winter. In late 2013, we had some space on an Illumina run with some other samples – and we sequenced the genome of this fungus. We’ve called it ‘Cairneyella’ after the late Professor John W. G. Cairney. There’s still much to learn about Cairneyella – and I’m seeking collaborators who’d like to share these last cultures and further the body of work on this remarkable fungus.

Event Date: 
Wednesday, May 28, 2014 - 19:00 - 20:00
Institution: 
USyd
Title: 

Population genetics and evolution of Cryptococcus gattii : an environmental pathogen

Abstract: 

The yeast species Cryptococcus neoformans and C. gattii cause cryptococosis in humans and a range of animal. Although research on Cryptococcus is generally structured in terms of its importance as a fungal pathogen, human infection is accidental and the fungus mostly lives as an environmental saprotroph. C. neoformans and C. gattii each comprise a number of distinct molecular genotypes that vary in their ecology, their geographic distribution, and various virulence-associated phenotypes. In particular, C. gattii molecular type VGII is responsible for outbreaks that have expanded the fungus beyond its normal geographic range. Our interests lie in understanding the ecology and evolution of C. gattii in the environment, and how these relate to its ability to cause disease. We have found the level of sexual recombination varies by molecular type, and that while in general C. gattii population structure is sexual, this is punctuated by periodic clonal lineages that may be associated with disease outbreaks. Here we refine our analysis using MLST data, haplotype networks and coalesence theory. We find the level of diversity within genotypes to be highly constrained and comparable to some recently evolved plant pathogens, and evidence for purifying selection at the master regulator of mating type. Comparison with other fungi that are causing major outbreaks suggests C. gattii outbreaks may be due to a “perfect storm”, where range expansion and elevated transmission combined with high virulence bring the fungus to new areas with deadly consequences. 

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