Quorum Sensing in Vibrios

Vibrio are Gram-negative bacteria commonly found in the marine ecosystem, and while some of them are virulent to human and animals, including aquatic animals, some are avirulent. Many vibrios are known to have group behavior for survival and virulence, such as biofilm formation, bioluminescence, swarming, toxin production, etc. Group behavior of the vibrios is mainly regulated by cell-to-cell communication, known as quorum sensing, in which bacteria can communicate through chemical compounds called autoinducers in a density-dependent manner. Three basic steps are involved in the quorum sensing process, i.e., synthesis of autoinducers followed by the active secretion or passive release of the inducers out from the bacterial cell. Subsequently, the signals are detected at the cell surface by membrane-bound receptor proteins which feed a common phosphorylation/dephosphorylation signal transduction cascade to control the expression of many genes including genes of virulence. The N-acyl homoserine lactone-dependent quorum sensing system was discovered first in Vibrio fischeri and Vibrio harveyi , and since then, quorum sensing has been described in many microorganisms including vibrios. We continue to discover its role in regulating virulence as well as its multitudinous environment. This chapter will give a brief insight on the quorum sensing in different Vibrios including V. fischeri , V. harveyi , and V. cholera .