Biology

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. 

Event Date: 
Wednesday, April 30, 2014 - 18:00 - 18:15
Institution: 
School of Biotechnology and Biomolecular Sciences UNSW
Title: 

The roles of extracellular DNA in bacterial biofilm formation

Abstract: 

Bacterial biofilm formation is dependent upon production of extracellular polymeric substances (EPS) mainly composed of polysaccharides, proteins, lipids and extracellular DNA (eDNA). eDNA promotes initial bacterial adhesion, aggregation, biofilm formation in a wide range of bacterial species. In Pseudomonas aeruginosa eDNA is a major component of biofilms and is essential for biofilm formation and stability. P. aeruginosa also produces phenazine an electrochemically active metabolite and phenazine production promotes eDNA release. The relationship between eDNA release and phenazine production is bridged via hydrogen peroxide (H2O2) generation and subsequent H2O2 mediated cell lysis and ultimately release of chromosomal DNA into the extracellular environment as eDNA. Recent investigation showed pyocyanin (a kind of phenazine predominantly produced by P. aeruginosa) binds to eDNA mediated through intercalation of pyocyanin with eDNA. Pyocyanin binding to DNA has significant impacts on DNA properties and also on P. aeruginosa cell surface properties including its hydrophobicity, attractive surface energies physico-chemical interactions and bacterial aggregation.

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

Genetic diversity of Group I Clostridium botulinum and Clostridium sporogenes

Abstract: 

Whilst classified as a single bacterial species, Clostridium botulinum comprises a phylogenetically and physiologically diverse collection of organisms. Members of this species are linked together based solely on the production of botulinum neurotoxin (BoNT); amongst most lethal natural toxin produced. Isolates that do not produce BoNT are taxonomically considered a separate species, such as Clostridium sporogenes. Given the species delineation is based solely on an unstable phenetic trait presents increasing challenges in a post-genomic era, particularly with increasing evidence pointing towards the lateral acquisition of BoNT production in many strains. Here, the pan-genome of Group I C. botulinum and C. sporogenes is presented, describing the genetic diversity of these species, highlighting the incongruent taxonomy of these organisms and presenting insights into the acquisition of BoNT within this group.

Event Date: 
Wednesday, April 30, 2014 - 19:00 - 20:00
Institution: 
Marie Bashir Institute for Infectious Disease and Biosecurity, Charles Perkins Centre, School of Biological Sciences and Sydney Medical School, The University of Sydney, Sydney, NSW 2006, Australia.
Title: 

The Greatest Experiment in Evolution: Viral Biocontrol of Rabbits

Abstract: 

The wild European rabbit (Oryctolagus cuniculus) was successfully introduced into Australia in 1859.  By the early 1900s rabbits had crossed the borders of all mainland states spreading at a rate of about 70 km a year, the fastest of any colonising mammal.  By the 1950s there may have been more than one billion rabbits in Australia.  The introduction of the rabbit has irrevocably changed the Australian landscape, significantly affecting both native flora and fauna.  Rabbits have therefore been vigorously targeted through the deliberate introduction of two viral control agents: Myxoma virus (MYXV) was successfully released in Australia in the 1950s, while Rabbit Haemorrhagic Disease Virus (RHDV) escaped from quarantine field trials in 1995.
 
Through the application of genome-scale phylogenetic methods I will describe the patterns, processes and outcomes of these unique and grand-scale experiments in evolution.  In particular, I will show how viral virulence has evolved in both cases (the example of MYXV in European rabbit is the canonical study of the evolution of virulence), and how phylogenetic methods provide a valuable insight into the genomic determinants of virulence evolution.  In addition, phylogenetic analysis of the spread of both MYXV and RHDV in the Australian environment provides key information on the rates, patterns and dynamics of pathogen evolution in a naïve environment, and represents a powerful analogy to cases of disease emergence following cross-species virus transmission to a novel host.
 
I will close by discussing the possible evolutionary consequences of the next grand viral biocontrol experiment planned for Australia: the release of Koi herpesvirus (KHV) to control the common carp that was also introduced to Australia in the 19th Century.

Event Date: 
Wednesday, March 26, 2014 - 19:00 - 20:00
Institution: 
UTS, Australia
Title: 

Feeling Hot Hot Hot: Insights on thermal regulation of microbial carbon fixation and metabolism in a warming ocean

Abstract: 

Ocean warming is expected to affect marine microbial phototrophs directly by influencing their metabolism and capacity for photosynthesis as well as indirectly through altering the supply of resources needed for growth. In turn, changes in phototrophic community composition, biomass and size structure are expected to have cascading impacts on export production, food web dynamics and fisheries yields, as well as the biogeochemical cycling of carbon and other elements. As a result, temperature is a critical parameter in coupled climate-ocean models because it influences not only the magnitude, but also the direction of future ocean productivity.
 
This seminar presents data from several recent oceanographic voyages to suggest that the statistically significant relationships found between temperature and carbon fixation of contemporary ocean microbes is confounded by the availability of co-varying light and nutrient resources, and challenges the notion that satellite-derived sea surface temperature is a suitable proxy for tracking changes in upper ocean biogeochemical function. It will also present laboratory data which demonstrates that thermal selection of photosynthetic microbes (over >100 generations) results in phenotypic trait evolution and shifts in photosynthesis:respiration. Collectively, these data show non-linearity in metabolism of photosynthetic microbes in a warming ocean, pointing to increased variability of responses and potentially less predictability in models.

Event Date: 
Wednesday, March 26, 2014 - 18:15 - 18:30
Institution: 
Radboud University Nijmegen, Netherlands
Title: 

The gut microbiome of phytopathogenic root fly larvae: insights into the detoxification of plant secondary metabolites by insect-associated microbes

Abstract: 

Plants of the genus Brassica produce various toxic compounds such as isothiocyanates in response to herbivore damage. Despite their toxicity, some insects can cope well with these compounds. One example is the larva of the cabbage root fly (Delia radicum) which is a serious agricultural pest. The mechanism by which these root feeding insects detoxify isothiocyanates is not explored. Our hypothesis is that microorganisms residing in the gut contain enzymes that break down the isothiocyanates and are thus crucial for survival of the root fly larvae. We substantiated this hypothesis by metagenome studies of the microbial gut community. Combined with functional screens of isolated gut microbes these analyses indicated that indeed the gut microbiota plays a vital role in the breakdown of isothiocyanates. Some genes encoding proteins that are involved in this process have already been identified. Ongoing genome and transcriptome studies of isolated gut microbes will enable us to find new candidate genes encoding proteins used for isothiocyanate breakdown that will subsequently be functionally characterized. This will lead to an in-depth understanding of the role of microbes in the plant secondary metabolite – insect interaction.

Syndicate content