March 2014

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.
 

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 - 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.

A massive thank you to everyone who helped organise and attended the JAMS workshop (TOAST) and the annual symposium and dinner. By all accounts people had fun and even learnt a things or two.