Chemical interplay and complementary adaptative strategies toggle bacterial antagonism and co-existence

Bacterial communities are in a continuous adaptive and evolutionary race for survival. A myriad of molecules that kill, defend, or mediate communication between bacterial cells of different lineages shape the final structure of the microbial community. In this work we expand our knowledge on the chemical interplay and specific mutations that modulate the transition from antagonism to co-existence between two plant-beneficial bacteria, Pseudomonas chlororaphis PCL1606 and Bacillus amyloliquefaciens FZB42. We reveal that the bacteriostatic activity of bacillaene produced by Bacillus relies on an interaction with the protein elongation factor FusA and how mutations in this protein lead to tolerance to bacillaene and other protein translation inhibitors. Additionally, we describe how the unspecific tolerance to antimicrobials associated with mutations in the glycerol kinase GlpK is provoked mainly by a decrease of Bacillus cell membrane permeability among other pleiotropic cellular responses. We conclude that nutrient specialization and mutations in basic biological functions are bacterial evolutive and adaptive strategies that lead to the coexistence of two primary competitive bacterial species rather than their mutual eradication.