Aggregation-mediated microcolony shields bacteria from contact-dependent competition and maintains phenotypic heterogeneity

Bacteria are adaptable microorganisms capable of surviving in a wide variety of environments. One common strategy for persistence and attachment to surfaces is the formation of microcolonies, often controlled by cell surfaces structures that mediate adhesion such as fimbriae. In this study, we show that type 1 fimbriae, and other adhesins structures such as autotransporter adhesins, trigger microcolony formation which confer resistance against a broad range of short-range contact-dependent weapons (e.g. T6SS, T4SS, CDI) but not against long-range diffusible weapons (e.g. diffusible toxins like colicins). Interestingly, we identify “sheltered” bacteria within microcolonies that benefit from collective protection without expressing the adhesive structure. Our findings demonstrate that adhesive structures not only improve survival in hostile environments by promoting microcolony formation but also maintain phenotypic heterogeneity within the microcolony, highlighting the importance of social behavior in bacterial adaptation to changing environments.