[Equipe Bonnefoy->article 92]
Key research interests
Microorganisms, such as Acidithiobacillus ferrooxidans and Thiomonas arsenitoxydans, thrive and play a key role in controlling the geochemistry of extreme habitats, characterized by acidic pH, low amounts of organic compounds and elevated concentrations of metals or metalloids.
A. ferrooxidans plays a major role in biomining processes by recycling ferric iron and sulfuric acid that chemically attack the mineral leading to the release of valuable metals.
T. arsenitoxydans is versatile since it is a moderate acidophile that can use both organic and inorganic substrates, though its most fascinating characteristics is that it is able to get energy from the oxidation of arsenite. In contrast, A. ferrooxidans grows only at very low pH by using inorganic substrates. This microorganism is able to live on rocks with "air du temps" fixing carbon dioxide and nitrogen gas and gaining energy from oxidation of reduced forms of iron and sulfur present in sulfidic ores.
The main topic of the group is to understand how these two Proteobacteria deal with their harsh environment, focusing on the oxidation of ferrous iron (Fe(II)) and sulfur compounds by A. ferrooxidans on the one hand, and of arsenite by T. arsenitoxydans on the other hand, using molecular genetics and functional genomics.
Current research projects
In T. arsenitoxydans, the electron donor present in the medium regulates the aio operon encoding the arsenite oxidase two subunits. We are interested in the regulation of this operon, and more particularly in the role played in the arsenic induction by the ArsR/SmtB metalloregulator family member encoded by this operon.
In A. ferrooxidans, the expression of the genes involved in Fe(II) and sulfur compound respiratory pathways is dependent on the electron donor present in the medium. In addition, the genes involved in Fe(II) oxidation are expressed before those involved in sulfur oxidation when both electron donors are present. We are studying whether the redox sensing sensor/regulator two-component system RegBA is responsible for this regulation since we have shown that (i) the redox potential increases during Fe(II) oxidation but remains stable during sulfur oxidation and (ii) the regulator RegA is able to bind to the regulatory region of a number of genes/operons involved in Fe(II) and sulfur oxidation.
Other research topics conducted with different partners include : (i) the anaerobic sulfur oxidation coupled to the dissimilatory iron reduction in A. ferrooxidans ; (ii) the quorum sensing regulon of A. ferrooxidans ; (iii) the adaptation to salt of Acidithiobacillus ferridurans and (iv) the analysis of the acidophilic iron and sulfur oxidizer A. ferrivorans CF27 genome sequence.