Quorum Quenching for Sustainable Environment

Quorum Quenching for Sustainable Environment

Sumira Malik, Shilpa Prasad, Tanvi Kumari, Shreya Ghoshal, Ankita Agrawal, Shashank Shekhar, Bijaya Samal
DOI: 10.4018/978-1-7998-7062-3.ch022
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Quorum quenching is the process that prevents quorum sensing through the disruption of signalling cascade and bacterial communication among themselves mediated by the degradation of the signalling molecules. Therefore, quorum quenching has a considerable contribution in the negative regulation of threatening diseases and eventually increasing soil reclamation through different mechanism mediated by microorganisms in reclamation of soil. Quorum sensing has a significant contribution in enhancement of soil quality through microbial-based enzymes and mechanism in the versatile fields which are a component of the environment. The current chapter discusses the details of various direct and indirect mechanisms mediated by microbial systems that have a significant role in soil reclamation for the sustenance of the environment.
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Quorum Quenching And Quorum Sensing Inhibitors

Several studies showed that there are a number of bacterial communities which are regulating and altering the gene expressions through the mechanism of Quorum sensing. They coordinate and regulate these processes with the help of QS signals either by host-micro interaction or microbe-microbe interaction (Grandclément et al., 2016).

The Quorum sensing mechanisms leads to the emergence of Quorum Quenching. Quorum Quenching is the environmental phenomenon of clearing or recycling of QS associated organisms by different mode of actions such as competitive inhibition, QS signal cleavage, etc. using different QQ chemical compounds or enzymes. The enzymes involved in the mechanisms of QQ are called as QQ enzymes and chemicals involved are called as QQ inhibitors (QSIs). Basically, all the mechanisms involved in the disruption of Quorum sensing are called as Quorum Quenching (Dong et al., 2001). Physical parameters also have a role to play in disturbance of QS signal pathways by altering pH and temperature (Byers et al. 2002; Delalande et al. 2005).

QQ Enzymes

Many studies have showed the degradation of N-acyl-homoserine lactones (AHL) by several enzymes. AHL is the QS molecule associated with gram-negative bacteria. The very first case of degradation in AHL was by the action of soil bacterial isolates of Bacillus and Variovorax genera (Dong et al. 2000; Greenburg et al. 2004). Mainly there are four catalytic classes involved in the degradation of AHL-cytochrome oxidases which are involved in the acyl chain oxidation (Chowdhary et al., 2007). Amidohydrolases which are involved in the breakdown of AHLs’ amide bond and releasing of homoserine lactone and fatty acid (Y.H. Lin 2003); reductases which are involved in the conversion of 3-oxo-substituted AHL to 3-hydroxyl-substituted AHL (Bijtenhoorn, P. et al., 2011) and lactonases which are involved in the opening of homoserine lactone ring (Zhang et al. 2002; Uroz et al. 2008).

In case of AHL degradation there are different architecture and amino acid sequence of enzymes involved in the process. Especially, in the case of lactonases, there are four families involved in the process varying in their structure and mechanisms. They are known as α/β – hydrolase fold lactonases, phosphotriesterase – like lactonases, paraoxonases and metallo – β – lactomase-like lactonases.

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