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and DSF based quorum sensing system are two best characterized examples of nonacyl HSL quorum sensing systems employed by plant pathogenic bacteria.
(i) Phc based quorum sensing system
PhcA, a LysR type regulator regulates the production of extracellular polysaccharides and enzymes involved in the pathogenicity of R. solanacearum (Chun et al.
1997). The activity of PhcA is negatively regulated by the two component system,
PhcS, and PhcR. This two component system is responsive to 3-hydroxypalmitic
Fig. 8.3 The regulation of acyl-HSL based quorum sensing. When the cell density is low, the
OHHL concentration does not attain a critical threshold level which leads to weak and insufficient
transcription of the genes for bioluminescence (luxICDABEG) for light emission (a). whereas at
high cell density, the OHHL concentration reaches a critical level to bind LuxR in order to stimulate transcription of luxICDABEG, leading to the emission of light (b)
8 Intrusion of Bacterial Quorum-Sensing for Antimicrobial Resistance Mitigation…