January 2013

Event Date: 
Wednesday, January 30, 2013 - 18:00 - 18:15
Institution: 
University Technology Sydney
Title: 

Development of an electrochemical biosensor for bacteria detection coupling immuno-capture with magnetic particles and amperometry at flow-channel microband electrodes.

Abstract: 

 
Current technology is insufficient for rapid on-site identification of the causative agents for waterborne diseases and existing time-consuming detection results in delayed management decisions. Fast, reliable and low-cost methods for the screening of pathogens are paramount in fields such as the environment, food industry, healthcare and defense. With the constant progress of scientific knowledge, a fast diversification of detection techniques is occurring, brought about by the appearance of imaginative new concepts within the scientific community. Biosensors are a perfect example of the combination of multidisciplinary knowledge. They encompass many fundamental, technological and scientific advances in biology, chemistry and physics.
Here, we describe a recently developed electrochemical biosensor for the detection of bacteria cells in aqueous samples. The technology used for this detection combines immuno-magnetic capture and amperometric detection in a one-step sandwich format, and in a microfluidic environment. The whole assay could be completed in 1 h and the experiments performed with Escherichia coli evidenced a linear response for concentrations ranging 102–108 cell ml−1.

Event Date: 
Wednesday, January 30, 2013 - 18:15 - 18:30
Institution: 
University of Western Sydney
Title: 

Changes in soil microbial community precede changes in plant community along a chronosequence

Abstract: 

Shrubs in semiarid ecosystems facilitate the establishment of other plant species under their canopies and promote changes in these understory plant communities as they grow. To better understand whether plant community dynamics are linked to changes in soil microbes, we characterized soil microbial communities in gaps (interspaces) and under Retama sphaerocarpa shrubs of three different size/age classes. Different methodological approaches including pyrosequencing of 16S rDNA, phospholipid-fatty acid (PLFA) analysis and microbial activity indicators were combined to characterize both the structure and function of microbial communities along the chronosequence. Small shrubs induced an increase in soil bacterial and fungal biomass, a stimulation of microbial activity and changes in the relative abundance of several bacterial groups, preceding aboveground increase in plant richness and biomass. Shrubs promoted a significant increase of Bacteroidetes, Betaproteobacteria and Gammaproteobacteria abundance in detriment of Actinobacteria and Firmicutes without changes in overall bacterial diversity. Some changes in the microbial community increased with shrub age while other did not, being microbial communities in gaps and under the canopy of large shrubs the most differentiated. We argue that the observed changes in composition and function of soil microbial communities may promote the increase in plant growth and understory species richness along the chronosequence. This emphasizes the importance of plant-soil interactions on defining the structure and composition of both plant and soil microbial communities and their impact on ecosystem functioning.

Event Date: 
Wednesday, January 30, 2013 - 19:00 - 19:30
Institution: 
University of NSW
Title: 

Who’s doing what? A metaproteomic survey of Southern Ocean microbes near Antarctica.

Abstract: 

The ocean around Antarctica is not just cold, it’s also dark for a large part of the winter.  This means that carbon fixation by photosynthesis is inhibited during the polar winter.  We used metaproteomics to reconstruct the ecology of microbes at the surface of the Southern Ocean near the Antarctic Peninsula, for both winter and summer seawater samples.  Metagenomics (community genomics) tells us what kinds of genes are present.  Metaproteomics goes a step further and determines which proteins (including enzymes) are actively being produced by microbes within a community.  Therefore, we can use this approach to reconstruct microbial processes used for carbon fixation, nutrient acquisition, and other metabolic pathways.  We found that ammonia-oxidising archaea were dominant at the Southern Ocean in winter, with the detected proteins indicating that they had a major role in ‘dark’ (light-independent) carbon fixation at the surface.  In summer, by contrast, these autotrophic archaea were undetectable at the ocean surface, when photosynthesis by algae was the major route of carbon fixation.  SAR11 bacteria (Pelagibacter spp.) were prevalent in both winter and summer, and detected proteins indicate that ATP-dependent uptake was important for the acquisition of nutrients by these heterotrophs, including simple organic compounds such as amino acids and taurine.  Flavobacteria (especially Polaribacter) were more prevalent in summer, and the detected proteins show that these heterotrophic bacteria use exoenzymes to target complex biomolecules (polypeptides, polysaccharides) released from decaying algae.  Overall, metaproteomics of the Southern Ocean surface has allowed us to identify the similarities and differences between winter and summer microbial communities, as well as which particular nutrients are being targeted by individual groups of bacteria and archaea.