The scientific project of our unit aims at studying the stimuli and conditions modulating gene flux frequencies (horizontal gene transfer and recombination, HGT) and consequently the relative impact of horizontal gene transfer on niche-specificity occupation (bacterial adaptation) and bacterial species definition. Two bacterial groups and their respective ecosystems will be approached: streptomycetes and the forest soil and streptococci and the oral cavity.
This project is built on our experience of molecular mechanisms of the fast bacterial evolution (genome plasticity, gene transfer). During the previous contract, new concepts and models have been developed about gene fluxes: accretion and mobilization by Integrated and Conjugative Elements, ICEs in Streptococci, insertion/deletion ‘indels’ and recombination gradients in terminal regions of the streptomycetes chromosome. Functional analyses also revealed that genes prone to HGT (e.g. transcriptional regulators, secondary metabolite biosynthesis gene clusters) impact variability and adaptation of bacterial strains to environmental stimuli.
Our objective is (i) to deepen our understanding of the molecular mechanisms of gene transfer (evolution and regulation of ICEs in streptococci, role of recombination homologous versus illegitimate in genetic variability in Streptomyces) and (ii) to study the impact of transferred genes on strain adaptation (e.g. commensal to pathogen life-style in streptoccoci, role of secondary metabolites in microbioal interactions in forest soil). On a long-term perspective, the aim is to understand the impact of these phenomana on niche adaptation and to identify the selective force driven by the environmental conditions (abiotic and biotic stimuli). In close collaboration with microbial ecologists, we will put these phenomena back into their ecological context (from ‘Petri dish to ecosystem’) to envisage their consequences in the frame of the emergence of new bacterial isolates and in microbial consortia structuring.