Screening Of QS Inhibitory Microorganism And Bioassay Of Clinical Isolates Of Pseudomona Aeruginosa

Recent study showed that some pathogenic bacteria of animal and plant regulate the expression of virulence factors with a mechanism of quorum sensing. The disruption of quorum sensing system may obviously reduce infection ability of these pathogens. Quorum sensing inhibitors function as a antivirulence drugs by disrupting QS system, rather than antibacterial drugs that kill bacteria. So it's not probable to induce bacterial resistance. Nowadays, screen of Quorum sensing inhibitors had become one of the hot points around the world.According to the characteristics of Quorum sensing noenzyme-inhibitors, a primary screening model in which Erwinia carotovora SCG1 was employed as a reporter and potato was used as testing plant, was established in this study. By the model, 312 strains, incuding 108 bacteria and 204 fungi, which have the activity on obviously inhibiting infection of E. carotovora SCG1, were obtained from 2,520 bacteria and 508 fungi. With inhibitory zone assay, three strains, B6-5, B38 and B35, which have no effect on growth of E. carotovora SCG1, were finally screened out, among them, the strain B6-5 which has the best effect on inhibiting infection caused by E. carotovora SCG1 was used to carry further validation and analysis of quorum sensing interference, and other isolates which inhibited the infection employing antibiotic production were laid off.Holes were punched on ABM assay agar mixed with appropriate number of reporter Agrobacteriun tumefaciens WCF47, AHL signal producing strain E. carotovora SCG1 or E. coli DH5a(pJZ365) and X-gal. Into the wells was placed 70μl of supernatant fluid subjected enzyme-inactive treating of strain B6-5. After 12 hours'cultivation, it was found that white zones, but not clear zones, appeared arround the wells contrast to blue background , and the well filled with LB fluid medium contral without it. This showed that activity production which interference QS system of carotovora SCG1 and E. coli DH5a(pJZ365) assuredly exit in the supernatant fluid, but it is diffcult to affirm the interference mechanism by inhibition of AHL generation or binding signal of receptor protein, or acceleration of receptor degradation, or other mechanisms.A. tumefaciens WCF47 (pCF372/pCF218) was inoculated in culture medium in which supernatant fluid subjected enzyme-inactive treating of strain B6-5 and AHL abstract were added. After 4 hour incubation, The activity of β-galactosidase was assayed. The result showed that The activity of β-galactosidase of sample have no...