Quorum Sensing and Signal Transduction in Biofilms: the Impacts of Bacterial Social Behavior on Biofilm Ecology

Abstract

The advances from at least two major research areas, biofilms and bacterial quorum sensing, have led us to begin to appreciate the concept that bacteria can organize into groups, form well-organized communities, and communicate with each other for coordinated activities or social life that was once believed to be restricted to multicellular organisms. Bacteria with altered physiological activities (biofilm phenotypes) are known to result largely from bacterial social behaviors controlled by quorum sensing or other mechanisms when they are living in biofilms. Understanding bacterial social behaviors and their molecular mechanisms in the development of biofilms will greatly facilitate the development of novel strategies in the prevention and treatment of biofilm infections. In 1998, researchers first described the role of las quorum sensing in biofilm formation of Pseudomonas aeruginosa. The biofilms formed by the mutant were also dispersed by the addition of the detergent sodium dodecyl sulfate. This finding suggests that quorum sensing plays an important role in the development of bacterial biofilms. More importantly, this study suggests an inextricable connection between two bacterial social behaviors, quorum sensing and biofilm formation. In P. aeruginosa organism, quorum sensing is highly complex and consists of two interlinked N-acyl-homoserine lactone (AHL) dependent regulatory circuits, which are modulated by numerous regulators acting at both the transcriptional and posttranscriptional levels. The chapter discusses how might quorum sensing signal molecules function in biofilms. Quorum sensing is emerging as an integral component of bacterial global gene regulatory networks responsible for bacterial adaptation in biofilms.