Abstract
Bacterial adaptability may be attributable to either fast changes in the gene expression processes or the fact that bacteria evolve very quickly because their short generation time and the large size of bacterial populations enable them to acquire particular adaptive skills. Studies on the links between evolutionary processes and bacterial adaptability were recently facilitated by advent of Next-generation sequencing methods (NGS). Interestingly, environmental genomics studies using these tools have shown that microorganisms belonging to the same species and showing less than 1% divergence in the nucleotide sequences of the genes encoding 16S rRNA (ecotypes) coexist in ecosystems. This microdiversity may lead to some functional diversity, since these strains may play different roles. /nUnderstanding the adaptability of bacteria to extreme conditions, such as those involving the presence of heavy metals, is crucial to be able to manage polluted environments such as acid mine drainage (AMD) and rock drainage. Bacteria of the genus Thiomonas are found ubiquitously in AMD as for example in the Reigous creek near Carnoulès, and contribute to the precipitation of arsenic, as they are able to oxidize arsenite (As(III)). In these ecosystems, considerable microdiversity has been observed in the Thiomonas genus as well as at the species level. Comparative genomic analyses showed that Thiomonas ecotypes have evolved by acquiring genomic islands giving them special abilities. These findings raise questions about the dynamics of Thiomonas adaptation and the corresponding processes. Thiomonas strains are able to form biofilms, and within these biofilms, the emergence of variants or cells that have acquired greater survival skills than to those of the starting population has been observed. These greater survival skills may be due to the existence of differences in gene expression or the acquisition or loss of genomic islands occurring in the biofilm. /nThe aim of the project entitled ""The role of biofilms in the adaptation and genomic variability of the Thiomonas bacteria involved in the natural mine drainage remediation processes"" is to identify the mechanisms involved in the emergence of variants in the biofilm which might explain how the Thiomonas bacteria evolve and adapt to these particularly toxic environments. For this purpose, various approaches will be used by the three partners to study the role of biofilms in the adaptation of Thiomonas ecotypes, including comparative and functional genomics (using NGS such as RNAseq and proteomics such as LC-SRM), genetic approaches (based on mutagenesis or complementation) and physiological analyses. This research will make it possible to determine the main factors favoring the emergence of stress-resistant variants in extreme environments and how biofilms contribute to these adaptive processes. /n
France