Isolation Of Biocontrol Bacteria By Quorum Sensing Mechanism And Studies In Its Properties

Quorum sensing is an environmental-signal-sensing system in bacteria. It is relies upon the interaction of a diffusible signal molecule with cell population density. Many bacterial important functions are regulated by quorum sensing, including bacterial bioluminescence, expression of virulence gene, antibiotic production, exoenxyme production, exoamylose production, plasmid conjugal transfer, and biofilm formation. The aim of this study was to build a good model of isolation of biocontrol bacteria by quorum sensing mechanism and studies in its properties.In the studying, 1511 bacterial strains was isolated from 154 soil samples collected from 39 towns in 13 countries of Han Nan and conserved by glycerol in low temperature condition. 62 strains of typeⅠbiocontrol bacteria which include aiiA gene and 42 strains of typeⅡbiocontrol bacteria which include ahlI gene were isolated by molecular biology technology as PCR technology. TypeⅠbiocontrol bacteria was strongly antagonistic Eriwinia carotovora subsp.carotovora, The antagonistic bacteria circle diameter of 36 strains were larger than 1cm, the largest strain is DZ122, its antagonistic bacteria circle diameter is 1.84cm. TypeⅡbiocontrol bacteria was strongly antagonistic Fusarium oxysporum f.sp. cubense, The antagonistic bacteria circle diameter of 25 strains were larger than 1cm, the largest strain is DFL059, its antagonistic bacteria circle diameter is 2.41cm.At present, the sequence of 16S rDNA provides a main basis on studying the systematic development of bacteria and building up the system of microbial taxonomy. This paper selected two strains of bacteria, which were antagonistic bacteria strongly than others, and analyzed their 16S rDNA sequence based on the general shape-analysis and biochemical-physiological features. The results showed that they were identified as Bacillus cereus Frankland, DZ122 and Pseudomonas fluorescens Migula, DFL059.The research showed that the optimal conditions of fermentation of DZ122 strain were as follows: culturing temperature 37+1℃, initial PH value 6～7, rotated 200r/min, seeding size was 3%(v/v), glucose as the carbon source, NH4Cl as the nitrogen source, C/N is 16, 300ml media in 500ml flask and incubated it for 20 hours. The optimal conditions of fermentation of DFL059 strain were as follows: culturing temperature 37+1℃, initial PH value 7～8, rotated 160r/min, seeding size was 1%(v/v), saccharose as the carbon source, NH4NO3 as the nitrogen source,C/N is 24, 50ml media in 500ml...