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Bacteria communicate within a system by means of a density dependent mechanism known as quorum sensing which regulate the metabolic and behavioral activities of a bacterial community. This sort of interaction occurs through a dialect of chemical signals called as autoinducers synthesized by bacteria. Bacterial quorum sensing occurs through various complex pathways depending upon specious diversity. Therefore the cognizance of quorum sensing mechanism will enable the regulation and thereby constrain bacterial communication. Inhibition strategies of quorum sensing are collectively called as quorum quenching; through which bacteria are incapacitated of its interaction with each other. Many virulence mechanism such as sporulation, biofilm formation, toxin production can be blocked by quorum quenching. Usually quorum quenching mechanisms can be broadly classified into enzymatic methods and non-enzymatic methods. Substantial understanding of bacterial communication and its inhibition enhances the development of novel antibacterial therapeutic drugs. In this review we have discussed the types and mechanisms of quorum sensing and various methods to inhibit and regulate density dependent bacterial communication.

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The present study was intended to optimize the quorum sensing inhibitory action of Solanum torvum root extract against Chromobacterium violaceum. Factors such as bacterial density, frequency of administration and concentration of extract were analysed. Plant samples were collected from Thrissur District, Kerala, India. Response surface modelling of factors by Box-Behnken approach was employed for optimizing quorum quenching activity of extract. The adequacy of mathematical model was verified by ANOVA and Cook’s distance table. Results revealed that quorum quenching property of Solanum torvum root extract is highly influenced by variables studied whereas maximum activity was found during administration of 300 µg/ml extract thrice in a day. It was also understood that extract does not possess any bactericidal activity wherein it only silence its quorum sensing mediated functions. This observations can be further used in quorum quenching studies.

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