Vesicle-enriched secretomes alter bacterial competitive abilities and are drivers of evolution in microbial communities.

Microbial membrane vesicles can carry compounds that inhibit bacterial growth, but how they impact the fitness of the vesicle-producing bacterial species and influence community dynamics remain unexplored questions. To address these questions, we examined the effect of vesicle-enriched secretomes (VESs) in different single-species and multi-species systems. Effects of VESs on single-species growth dynamics were determined for nine bacterial species belonging to four genera (Escherichia, Salmonella, Pseudomonas and Bacillus) in nutrient-rich and poor growth media. Results showed both species-specific and nutrient-dependent effects of the VESs on bacterial growth. The strongest antagonistic effects were observed for VES isolated from the natural isolates of E. coli, while those isolated from P. aeruginosa PA14 affected the highest number of species. We further demonstrated that these VESs altered the competitive abilities of the species involved in two-species (S. Typhimurium LT2 and S. arizonae) and three-species systems (E. coli, S. Typhimurium LT2 and B. subtilis). Finally, using experimental evolution we showed that different bacterial species could rapidly acquire mutations that abrogated the antagonistic effects of VESs. This study demonstrates how VESs can contribute in shaping microbial communities, both by increasing the competitive ability of a given bacterial species and as a driver of genetic adaptation.