Quorum Sensing: Melody Beneath the Ground

Quorum sensing (QS) systems allow bacterial organisms to coordinate their behavior depending on the local population density and are used in many artificial systems requiring cell-to-cell communication. The accumulation of optimum stimulatory levels of autoinducers is detected by bacteria that affect the gene expression of their behavior. QS bacteria defer the production of virulence factors until cell numbers reach optimum levels, resulting in infection leading to activation of the host immune system by secretion of virulence factors causing productive infection. It is a successful technique that coordinates the gene expression of groups of organisms. In this chapter, the mechanisms pertaining to varied bacterial QS systems are presented and discussed. The differences between two definitive bacterial signal transduction systems are also discussed. We contend that the bacterial QS systems are optimally intended to specifically translate extracellular autoinducer information into internal changes via gene expression. In addition, the different bacterial QS systems used in deciphering basic mechanisms underlying the advancement of bacterial communities are discussed. Here, we review the updated advancements of the genetic approaches in engineering QS circuits to utilize bacterial communication in environmental biotechnology.