AbstractThe sociobiology of bacteria, largely unappreciated and ignored by the microbiology research community two decades ago is now a major research area, catalyzed to a significant degree by studies of communication and cooperative behavior among the myxobacteria and in quorum sensing (QS) and biofilm formation by pseudomonads and other microbes. Recently, the topic of multicellular cooperative behaviors among bacteria has been increasingly considered in the context of evolutionary biology. Here we discuss the significance of two recent studies1,2 of the phenomenon of “cheating” mutants and their exploitation of cooperating microbial populations of Pseudomonas aeruginosa. BioEssays 30:296–298, 2008. © 2008 Wiley Periodicals, Inc.