Microbiology

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 - 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, 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.

Event Date: 
Wednesday, March 26, 2014 - 18:00 - 18:15
Institution: 
UNSW
Title: 

Insights into the stress response of the biomining bacterium Acidithiobacillus ferrooxidans using gene expression and proteomic analysis

Abstract: 

Bioleaching is a simple and effective process used for metal extraction from low grade ores and mineral concentrates using microorganisms. The extraction of some metals such as copper from low grade ore is becoming necessary because of gradual depletion of high grade ore. The traditional methods used for extraction of copper are either Pyrometallurgy or Hydrometallurgy. However both the methods are not environmental friendly. There are many techniques proposed to extract metals but these are not practically suitable, as these requires a very high energy input as well as most of them creates environmental pollution problem, that also rises the cost of environmental protection throughout the world. Therefore, bioleaching is recognizable as the most environmentally friendly method of separating metals since it requires less energy and it reduces the amount of greenhouse gasses released to the atmosphere. Bioleaching is also a fairly simple process that does not require a lot of expertise to operate or complicated machinery.
The most commonly used bacterium in bioleaching is Acidithiobacillus ferrooxidans (former Thiobacillus ferrooxidans) and this is due to its capacity to oxidize metal sulphides. A. ferroxidans is a chemolithotrophic bacterium capable of utilizing ferrous iron or reduced sulphur compounds as the sole source of energy for its growth. It thrives optimally around pH 2.0 and 30ºC. During Bioleaching process, A. ferrooxidans is often subject to changes in the ideal growth pH and temperature, and to nutrients starvation. These changes can affect the bacterial physiology and as a consequence, the efficiency of bioleaching. Then, the stress response of this bacterium subject to heat stress and phosphate starvation has been investigated using different approaches, namely, gene expression and proteomic analysis, Fourier transform infrared spectroscopy (FT-IR), as well as morphological analysis by scanning electron microscopy (SEM).
The results showed that under the tested stress conditions A. ferrooxidans cells suffer elongation, a common stress response in bacteria. Alterations in carbohydrates, phospholipids and phosphoproteins were detected by FT-IR. By proteomic analyses (2-DE and tandem mass spectrometry), many differentially expressed protein spots were visualized and identified as proteins belonging to 11 different functional categories. Indeed, the up-regulated proteins were mainly from the protein fate category. Real time quantitative PCR was employed to analyze changes in the expression patterns of heat shock genes, as well as many other genes encoding proteins related to several functional categories in A. ferrooxidans. Cells were submitted to long-term growth and to heat shock, both at 40°C. The results evidenced that heat shock affected the expression levels of most genes while long-term growth at 40°C caused minimal changes in gene expression patterns – with exception of some iron transport related genes, which were strongly down-regulated. Further bioinformatic analysis indicated a putative transcriptional regulation, by the σ32 factor, in most heat-affected genes. These results evidence that A. ferrooxidans has an efficient range of stress-responses, which explains its ability for biotechnological purposes.
 

Reference: JOB391
Location: Sydney, NSW, Australia
Employer: Hawkesbury Institute for the Environment, University of Western
Application deadline: CLOSED
Syndicate content