August 2013

Event Date: 
Wednesday, August 28, 2013 - 19:00 - 20:00
Institution: 
iThree Institute UTS
Title: 

Genome plasticity in Vibrio species – how lateral gene transfer directs niche specialisation and pathogenicity

Abstract: 

Bacteria of the Vibrio genus are abundant in aquatic environments, fulfil important nutrient cycling roles and are often found in association with marine animals such as corals, molluscs, sponges, crustaceans and fish. This diversity in niche occupation is a feature of Vibrio species and is largely (or at least in significant part) driven by lateral gene transfer (LGT). LGT is a two-step process firstly requiring physical transfer of DNA from one bacterial cell to another followed by subsequent integration of the transferred DNA into the genome thus allowing stable inheritance and expression. Numerous mechanisms for integration exist such as homologous recombination and a wide-range of diverse genetic elements such as transposons, integrative conjugative elements, prophages and integrons. Using two Vibrios species, V. rotiferianus and V. cholerae, research in our laboratory has sought to understand how mobile DNA contributes to vibrio evolution, niche specialisation and pathogenicity. In V. rotiferianus, we have been researching the integron, a genetic element that contributes up to 3% of a vibrios genome in laterally acquired mobile DNA. This region is dynamic and evolves at a faster rate than mutation. Our research has shown that this region provides the organism a mechanism for reworking surface polysaccharide affecting biofilm formation and potentially interactions with higher organisms. Furthermore, we have been researching evolution in V. cholerae isolated from Sydney estuarine waters. These isolates are pathogenic in animal models with all lacking the usual virulence factors of cholera toxin and colonisation factor tcpA and most lacking type III secretion indicating the presence of novel virulence factors. One isolate we are focussing on contains a novel 32-kb mobile element inserted into the indigenous recA but carries a unique recA with only 80% identity to other V. cholerae recA genes. Overall, our research demonstrates the plasticity of vibrio genomes and the significant contribution that LGT makes to the continuing evolution to the Vibrio genus.

Event Date: 
Wednesday, August 28, 2013 - 18:00 - 18:15
Institution: 
CSIRO Canberra
Title: 

Decomposer Microbial Communities Shift from Native Eucalyptus Diversity to Pine-type Diversity in Eucalypt Forests Fragmented by Pine Plantations

Abstract: 

 
The Wog Wog Fragmentation Experiment was started 29 years ago as a collaboration between CSIRO and NSW Forestry and is one of the longest running ecological experiments in the world.  It was designed to study the effects of Pinus radiata plantations on patches of old-growth Eucalyptus forest in terms of overall health as well as plant and insect species diversity.  Early work at the site showed that, in agreement with fragmentation ecology theory, predatory and generally rarer beetles decreased in eucalyptus fragments surrounded by the newly planted pines whereas decomposer and fungus-feeding beetle species increased.  These types of edge-dependant effects penetrated at least 100m into remnant eucalyptus forest fragments.
Recently, there have been a number of new studies on diverse aspects of forest diversity and health at the site.  This recent work has focused on understory plant diversity, long-term ground-dwelling beetle diversity and population dynamics, soil nutrient levels, soil bacterial and fungal diversity, skink and bird diversity, Eucalyptus growth and demographics, and understory light and temperature regimes.  Andrew King’s presentation will focus on the interaction between soil microbial communities, altered soil carbon and nitrogen cycles, and an unexpected increase in Eucalypt growth in response to fragmentation.

Event Date: 
Wednesday, August 28, 2013 - 18:15 - 18:30
Institution: 
CSIRO Canberra
Title: 

Multi-scale spatial patterns of soil microbial communities and biogeochemical processes in three arctic ecosystems

Abstract: 

Microbial communities and their functional role in soil biogeochemical processes vary across spatial scales. Although soil and microbial spatial variability has been studied in various tropical and temperate ecosystems, little information is available from arctic ecosystems. Arctic soils represent a significant proportion of global land mass and contain about one fourth of total soil carbon pool. Soil microbial nitrogen (N) transformations such as nitrification and denitrification have significant implications for N availability and N loss in nutrient-limited arctic ecosystems. This study explored the spatial relationships among microbial communities, functional processes and soil properties in three Canadian arctic ecosystems. Despite adverse climatic conditions and frequent cryopedogenic processes, soil attributes and microbial abundance are highly spatially structured and their spatial autocorrelation is consistent within and between the ecohabitats. However, the zone of spatial autocorrelation is substantially smaller than non-arctic ecosystems. Ammonia-oxidizing and denitrifying communities are spatially structured within 5 m whereas potential nitrification and denitrification are spatially autocorrelated within 40 m in arctic soils. Nitrification activities are driven at small scales (<1 m) by moisture and total organic carbon content whereas gene abundance and other edaphic factors drive at medium (1-10 m) and large (10-100 m) scales. Soil moisture, organic carbon and nitrogen content are the predominant driving factors with nirK abundance also correlated to denitrification across spatial scales. Overall, this study unravels the multi-scale determinants of nitrification and denitrification in Arctic ecosystems.

REPORT
Mike Manefield

Amazing turn out for JAMS last night at the Australian Museum. Three excellent presentations from Nathan Lo (Blattabacterium genome evolution - USyd), Tom Jeffries (Sydney Harbour Microbiome - UTS) and Yit Heng Chooi (Fungal metabolite genetics and biochemistry - ANU). The audience was also on the money with probing questions reassuring the speakers that their labours are well appreciated by an elite body of microbiology professionals.

The idea of a two day microbial community analysis workshop was also re-introduced and planning for this has commenced. A call is also out for volunteers for the Australian Museum Sciecne Festival (10th August, 13th-15th August and 20th-22nd August).

Please email Mike Manefield if you're interested. As of the 1st of August, we still need around 10 more volunteers.