Biofilms: Maintenance, development, and disassembly of bacterial communities are determined by QS cascades

Unicellular organisms use a variety of mechanisms to coordinate activity within communities, called biofilms, and across species to accomplish complex multicellular processes (Aguilar et al., Curr Opin Microbiol 10:638–643, 2007; Kolter and Greenberg, Nature 441:300–302, 2006; Miller and Bassler, Annu Rev Microbiol 55:165–199, 2001; Stoodley et al., Annu Rev Microbiol 56:187–209, 2002). Informed by chemical communication, motile cells of the Bacillus subtilis and filamentous cells of the Streptomycetes organize themselves into conspicuous multicellular structures that carry out specialized tasks in spore formation and dispersal. Furthermore, most bacteria have evolved elaborate mechanisms for adhering to solid surfaces and thereby establishing complex communities referred to as biofilms. Importantly, QS cascades are essential for the formation of bacterial multicellular communities and complex biofilms. This chapter focuses on the major QS systems, playing an active role in the rise of complex bacterial communities in different bacterial models.