Screening Of Bacterial Quorum Sensing Effector From Chinese Traditional Medicinal Materials

Quorum sensing (QS) is a community genetic regulation mechanism that controls microbiological functions according to the cell density. Bacteria with QS can produce and release a kind of signal molecule called autoinducer, which increases simultaneously with the increasing of cell density. When the autoinducer accumulates to a certain degree, it will change some specific gene expression of the bacteria, and thus in turn has influence on the microbiological function including intergrowth, bacteria virulence, cell competition, antibiotics producing, spore mobility and biofilm formation. Because bacterial QS effector can regulate and control bacterial behaviors, screening them has important biological significance and applicable value.This article screens natural bacterial QS effector from Chinese traditional medicinal materials with the indictor bacterium C. violaceum CV026, which secretes violacein with outside AHLs but doesn't produce AHLs. It firstly establishes the approach to extract AHLs and AHLs plate assay, then discusses the factors effect semi-quantitative measure AHLs, and finds using ethanol to dissolve violacein is better than using water-saturated butanol to extract violacein, the best content of ethanol in water to dissolve purple pigment is 55.6%, and the optimal wavelength is 580nm.Study on screening QS effector from Chinese traditional medicinal materials indicates: compared to adding AHLs alone, eight materials, including forsythia, added with AHLs inhibit CV026 to secrete violacein, therefore they may produce compounds inhibit QS; three materials, including herba houttuyniae, honeysuckle and bupleuri, added with AHLs can stimulate CV026 to secrete more violacein comparing with adding AHLs alone, so they may contain AHLs biomimic. And the research proves these QS effector in materials come from the materials themselves, not because bacteria contamination from outside environment. Herba houttuyniae contains some compounds can cooperate with AHLs to enhance CV026 to secrete violacein, but not AHLs biomimic. Honeysuckle and bupleuri can make CV026 to secrete violacein alone, they may contain AHLs biomimic. And bupleuri contains more AHLs biomimic than honeysuckle. Besides, the method to extract AHLs biomimic from bupleuri is explored. With water as extract solvent, bupleuri dipped in it for three days can get most AHLs biomimic. With hexyl hydride to get rid of nonpolar substance, and then acetic acid to backextract, relative high purity AHLs biomimic can be got from the water extraction solution. Futher research indicates water solution with AHLs biomimic from Bupleuri is acidic(pH1), and these biomimic are sensitive to alkali circumstance, but stable in high temperature.