Isolation And Characterization Of Microbes Containing Quorum-quenching Enzymes

Bacterial Quorum-sensing,in which N-acyl homoserine lactone (AHL) acts as a key singnal is involved in regulation of diverse biological function,including production of virulence factors and bioflim formation of human pathogens. Several groups of AHL-degradation enzymes have recently been identified in a rang of living organisms including bacteria and eukaryotes.Expression of these genes encoding AHL-dagrading enzyme in AHL-dependent pathogens and plants efficiently quench the acceleration of QS signal and blocks pathogenic infection.Discovery of these novel quorum quenching enzymes has not only provided a promising means to control bacterial infections.but also presents new challenges to investigate their roles in host organisms and their potential impact on ecosystems.Two strains XI and Rl which could degrade AHL were isolated in this study.Accroding to their morphology,and biochemical properties.and 16SrDNA, 18SrDNA sequence analysis.the strain of XI is identified as Xanthomonadaceae genus and the strain of Rl is identified as Rhodosporidium genus.the 18SrDNA of strain Rl shared 99.9% sequence identities with that of Rhodosporidium toruloides,The optimal cultivatation temperature is 28-30℃ and pH7.5 for both strains.The results of utilizing different AHL as sole carbon and energy source by both strains suggest that CFU of the strain is effected by the count of carbon atom on the N-linked acyl chain. Analysis is antagonist on the virulence of Erwinia carotovora showed that either the strain culture broth.or the crude enzymes of the strains have the ability to quench the quorum-sensing and attenuate the virulence of Erwinia carotovora.