April 2014

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, 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 - 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.