AI-2 dependent cell to cell language regulates social behavior and development in Bacillus subtilis

LOMBARDIA, E.; ROVETTO, A.; ROBERTO RICARDO GRAU

Viena

Congreso; 11th International Congress on Microbial Ecology; 2006

AI-2-DEPENDENT CELL TO CELL LANGUAGE REGULATES SOCIAL BEHAVIOR AND DEVELOPMENT IN BACILLUS SUBTILIS   Esteban Lombardía, Luciana Pretto, Adrián J. Rovetto and Roberto R. Grau* Departamento de Microbiología, Facultad de Ciencias Bioquímicas y Farmacéuticas FCByF-UNR e Instituto de Biología Molecular y Celular de Rosario, IBR-CONICET. Suipacha 531 – Rosario (2000) - Argentina Phone: (54) 341-4353377. E-mail: estebanlom@mixmail.com         ABSTRACT   Cell to cell communication in bacteria is mediated by quorum sensing systems (QSS) that produce chemical signal molecules called autoinducers (AI). In particular, LuxS / AI-2 dependent QSS has been proposed to act as a universal lexicon that mediates intra- and inter-specific bacterial behavior. Here we report that the model organism B. subtilis operates a luxS-dependent QSS that regulates its morphogenesis and social behavior. We demonstrated that B. subtilis luxS is a growth-phase regulated gene that produces active AI-2 able to mediate the inter-specific activation of light production in Vibrio harveyi. We demonstrated that in B. subtilis, luxS expression was under the control of a novel AI-2-dependent negative regulatory feedback loop that indicated an important role for AI-2 as a signaling molecule. Even though luxS did not affect spore development, AI-2 production was negatively regulated by the master regulatory proteins of pluricellular behavior, SinR and Spo0A. Interestingly, wild B. subtilis cells, from the undomesticated and probiotic B. subtilis natto strain, required the LuxS-dependent QSS to form robust and differentiated biofilms and also to swarm on solid surfaces. Furthermore, LuxS activity was required for the formation of sophisticated aerial colonies that behaved as giant fruiting bodies where AI-2 production and spore morphogenesis were spatially regulated at different sites of the developing colony. We proposed that LuxS / AI-2 constitute a novel form of quorum sensing regulation where AI-2 behaves as a morphogen-like molecule that coordinates the social and pluricellular behavior of B. subtilis.