Stress responses modulate bacterial competitive fitness in polymicrobial communities

Stress responses are crucial for bacterial survival under adverse environmental conditions. The underlying mechanisms encompass complex networks of signal sensing and transcriptional and posttranscriptional regulation. These responses are traditionally studied in individual species by exposing cells to various environmental stresses, but now it has become more evident for their indispensable roles in interspecies interactions in complex microbial communities. Both general and specific stress responses have been implicated in helping cells survive external attacks from neighboring species that can translocate antibacterial compounds or toxic effectors. These effectors can target multiple essential functions and induce diverse protective stress responses, some of which resemble the innate immunity protection of eukaryotes while others rely on specific toxin-antitoxin interactions for protection. Therefore, stress responses are not a seemingly passive armor but play crucial functions in the competitive fitness of microbes living in complex communities.