Studies of social behavior in bacteria have begun to clearly shape how microbiologists perceive microbial communities. The relationship between QS and biofilm formation has the potential to shape these communities. Closely related species seemingly employ QS for very different purposes during biofilm development.

Many environments are colonized by biofilms consisting of multiple species. In this context, the likelihood of interspecies interactions in the form of QS signaling may be high. Cooperative QS signaling has been demonstrated in several multispecies biofilm systems (McNab et al. 2003; Burm0lle et al. 2006). In some cases, QS appears to be utilized by microbes to compete with one another. Biofilms probably represent a common relevant context for these types of interactions.

Microbial biofilms have strong relevance to chronic bacterial infections (Parsek and Singh 2003; Hall-Stoodley et al. 2004). Since biofilm formation for many organisms are QS-mediated, therapeutic strategies targeting QS systems are attracting attention in the drug development fields. Microbes have long utilized various anti-QS strategies for competition against other species (Zhang and Dong 2004). Understanding these molecular mechanisms may be fruitful in developing therapeutic strategies against pathogenic species. Already, some quorum-quenching chemical compounds have demonstrated success in inhibiting microbial biofilms (Dong and Zhang 2005). Unlike modern antibiotics, QS-directed therapies are not designed to cause bactericidal or bacteriostatic effects, and thus, emergence of resistance may be less problematic. Anti-QS measures have been demonstrated to be effective for plant infections. Heterologously expressed AHL-lactonase rendered tobacco and potato plants significantly more resistant to Erwinia caro-tovora (Dong et al. 2001).

As the studies of microbial communities continues, understanding how different species percieve and respond to one another will be crucial to understanding community composition and function. The most relevant context for such studies may be microbial biofilm.

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