Cellular interactions in singles- and mixed-species biofilms of bacillus subtilis

Microbiology has had a profound impact on human societies and interests. It has provided solutions for diseases and changed entire industries. In nature, microorganisms commonly live in sessile communities called biofilms. These communities have high cell densities that promote the development of communications networks based on signaling molecules, and also allow for complex interactions to form among cells forming part of the biofilm. Furthermore, cells living in natural environments are often exposed to members of other species, which may become collaborative partners, or compete for resources. The recent development of better molecular biology tools and more sophisticated microscopy techniques, along with the application of social theory and big-data informatic approaches to the study of large microbial populations has brought forward the novel field of sociomicrobiology, which tries to better understand how microbes interact with one another. This dissertation presents a comprehensive review of the current knowledge of the development of biofilms by the Gram-positive model bacterium Bacillus subtilis, with a focus on the mechanisms and signals that mediate the interactions that this bacterium can establish, both among its own cells and with those of other species. It includes original research on the interactions that B. subtilis can develop with other soil bacteria, both as active members of a predator-prey relationship, and as providers of environmental cues that change the structure of B. subtilis biofilms. Additionally, the present work includes investigations on the genetic differences between B. subtilis strains and strain variants that impact phenotypic social behavior and biofilm formation. This dissertation also includes the first comprehensive inquiry about the total effect that a family of regulatory phosphatases has upon the population heterogeneity of B. subtilis and its adaptability to diverse environments and growth conditions.