Quorum-sensing network-associated gene regulation in Gram-positive bacteria

Quorum sensing (QS) is the chemical communication processes between bacteria, which may be inter-genus or intra-genus. In general, several physiological functions, such as nutrient uptake, competence development, biofilm formation, sporulation, and toxin secretion, are accomplished through QS process. The QS (cell density-dependent process) circuit in Gram-positive bacteria consists mainly of two parts: an inducer molecule and a receptor protein. The binding of inducer molecule to receptor activates the target gene, which then performs the necessary function in bacteria. In the past few years, several investigations have been conducted to explore the QS circuit in various bacteria, but still this information is insufficient to fully understand the bacterial gene expression cascade. In the present review, we summarize the QS architecture and their associated gene regulation in four Gram-positive bacteria, such as Bacillus subtilis, Staphylococcus aureus, Bacillus cereus, and Streptococcus pneumoniae. It is well established that S. aureus, B. cereus, and S. pneumoniae are potent human pathogen. A detailed understanding of QS circuit in these bacteria would be useful in preparation of customized medicine in future. Whereas, B. subtilis is an industrially important candidate and has been used in several biotechnology sectors. Understanding of QS circuit in B. subtilis will definitely enrich the antibiotics and enzyme industries.