Screening Of Soil Bacilli And Identification Of A Pseudomonas Sp. Inhibiting Quorum Sensing

With the extensive use of antibiotics, bacterial resistance has become a major problem in hospital. Antibiotics are currently used to to achieve the anti-infection by direct inhibition of microbial growth, with the pressure to survival, which can easily lead to drug resistance. Therefore, finding new solutions to treat bacterial infections are becoming hot spots. In Pseudomonas aeruginosa, the production of many virulence factors and secondary metabolites is regulated in concert with cell density through quorum sensing. Two quorum-sensing regulons have been identified in which the LuxR homologues LasR and RhlR are activated by N-(3-oxododecanoyl)-L-homoserine lactone (3-oxo-C12-HSL) and N-butanoyl-L-homoserine lactone (C4-HSL) respectively. The discovery of QS system has triggered researches for anti-QS compounds by chemical synthesis and from natural products.In this work, the screening systems was constructed, which enabled us to identify a number of bacteria with anti-QS activity from soil. The ability of microbe to inhibite rhl system in QS was screened by agar plate assay using the Chromobacterium violaceum CV026reporter strain (a mini-Tn5mutant). Varing levels of inhibition ware shown in the screening. In the priliminary screening,56strains from about7000bacteria inhibited violacein production, and16strains promoted it. Culture extracts of13strains exhibited a notable inhibition in the secondary screening. Our study focused on a Pseudomonas sp. that is phylogenetically affiliated by16S rRNA gene sequence. It was shown that the culture extract can significantly reduce the production of virlence factors, suggesting a direct or indirect interference on QS sysetem. Further studies are required to isolate specific active substances from the strain extract.