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Chapter 2 : Multicellularity and Biofilms
Category: Environmental Microbiology; Microbial Genetics and Molecular Biology
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The authors argue that multicellularity is chiefly characterized by extensive intercellular interactions that lead to coordination of the cells’ activities. They also argue that the evidence collected on biofilms thus far only partially supports the assertion that biofilms are multicellular organisms. In addition to extensive intercellular interactions, the classical examples of bacterial multicellularity also feature coordination of the activities of constituent cells. The chapter focuses on multicellularity of biofilms. Intercellular signaling is likely involved in establishing the division of labor, because quorum-sensing signals are known to be required for efficient sporulation. This division of labor could benefit the biofilm as a whole, because one can speculate that Bacillus subtilis fruiting bodies play a role in spore dispersal, a function proposed for myxococcal fruiting bodies and the aerial hyphae of streptomycetes. In this way B. subtilis biofilms can be said to show all the features characteristic of multicellularity: intercellular interactions that lead to a coordination of cell activities that benefits the community. Perhaps the most daunting challenge in studies relating to bacterial multicellularity will be to determine whether an observed coordination of cell activities actually benefits the biofilm community as a whole. In large part, this is because biofilms typically lack an obvious function. A potential solution to this problem is suggested by the observation that terminal differentiation is a feature common to several of the examples of bacterial multicellularity discussed in this chapter (e.g., heterocysts, aerial hyphae, and myxobacterial fruiting bodies).