Introduction As for plants or animals, the microbes form populations that consist of interacting individuals from the same species. This level of organisation is an operating unit able to respond to biotic stresses coming from other ecological co-inhabitants such as microbes or plants. The sum of these interactions (often occurring at the cellular level) drives responses and ecological traits at higher scales such as in the forest ecosystem. Question The global aim of this project is to assess how a microbial population affects its biotic co-inhabitants in a forest soil and how in return these latter influence the dynamic of the bacterial population. In this study, we focused on this last point and investigated the genomic diversity of a Streptomyces population isolated from grains of rhizospheric soil. Results We selected strains that could be considered as clones, sequenced and compared their genomes. We showed that their genomes presented an unexpectedly large set of variable genes (ca. one third of the population pangenome) indicating that this population had a great evolvability over a short evolutionary time. We showed that this rapid genome dynamics (massive gene fluxes fuelled by mobile genetic element mobility) in bringing different functions in individuals of the population, can help to its functioning. For instance, some metabolites produced by some individuals provide advantage to non-producing conspecifics (public good) in biotic competition. Conclusion These massive gene fluxes do not occur at long-term evolutionary time but at a scale enabling the population response to environmental changes. This tremendous capacity of evolvability appears as a key factor to favour resilience of the e