Inhibition of Quorum Sensing Activity by Ethanol Extract of Scutellaria baicalensis Georgi

Over a 30-year period, it has become apparent that a diversity of bacterial species commonly control expression of gene circuits in a population-dependent manner via a regulatory mechanism known as quorum sensing (QS). In QS, small diffusible molecules called autoinducers mediate the ability to monitor the size of a bacterial population [1-3]. Autoinducers produced by bacteria diffuse out and accumulate in the surrounding environment, and once a threshold concentration has been reached, they diffuse back into the bacteria and regulate the transcription of specific genes. Increasing evidence indicates that bacterial QS is involved in the regulation of diverse biological processes including exopolysaccharide synthesis, virulence factor gene expression, sporulation, biofilm formation, motility, bioluminescence and antibiotic biosynthesis [4-7]. In Gram-negative bacteria, N-acyl homoserine lactones (AHL) are most commonly used as signal molecules, and the AHL-mediated QS plays an important role in regulating virulence factors, for example extracellular enzyme production in Pectobacterium carotovorum subsp. Carotovorum (P.c.c.), conjugation in Agrobacterium tumefaciens and toxin production in Burkholderia glumae [8,9].