Strains Screening Of4Antibiotic-resistance Mutate And Study On Antimicrobial Activity Of Xenorhabdus Bovienii YL002

The metabolites of symbiotic bacteria associated with entomopathogenic nematodesown much bioactivity have application in many aspects such as insecticidal, antifungal,antibacterial, antivirus and anticancer, that make it become a kind of new bioresource withhigh potential for development. X.bovienii YL002was obtained from the entomopathogenicnematodes screened from Yangling, Shaanxi, previous research improved that themetabolites showed obvious antimicrobial activity. But there is a low production ofnematodes of almost all the wild strains screened from natural environment, this situationgoes against the further study and industrial output. Contrapose this problem we treated theYL002wild strain with UV and acridine orange combined to obtain mutate strains withresistance of4antibiotics respectively. The antimicrobial activity of the metabolites, cultureand the differences of DNA of the mutate strains were studied. Main results and conclusionsare as follows:1.89mutant strains with antibiotic resistance were obtained with UV and acridineorange combined,17mutant strains with genetic stability were selected through thefollow-up test.2. The inhibit effect on Bacillus subtilis of17mutant strains were tested by agardiffusion method,9of them have a stronger inhibit effect, L0420-3showed the strongestinhibit effect, the variation rate of the diameter of inhibition zone were above80%; mutantL8, L2-1, L0314-4and H0408-6showed no inhibit effect on Bacillus subtilis. But mutantL0314-4showed stronger inhibit effect on Botrytis cirerea, the growth inhibitory rate was74.85%, which was1.33times of YL002, while L0420-3was only50.60%; mutantQ0104-1showed stronger inhibit effect on Sclerotinia sclerotiorum, the efficacy was1.34times and1.16times of YL002respectively in potted plant experiment.3. The culture feature of some mutants has changed. On NA flat, the colonies ofYL002were white and translucent, moist, circular with an regular margin; colonies ofmutant Q025-2were orange, much flatter with an irregular margin, and the diameter wasmuch greater; the color of colonies of mutant Q025-7were rose pink; colonies of mutant L0420-3were white and opaque, dry, and inward flange was convex. The amount of growthof mutant Q1207-1was decreased obviously, logarithmic phase was delayed and stationaryphase was bring forward.4. The component of the ethyl acetate extracts of5mutant strains were comparedwith YL002by HPLC, the result showed that both the component and content has changed.5. There was variation in the DNA of mutant strains and wild strain. The geneticdiversity of2mutant strains was studied by AFLP,48of64selective primer pairs amplified1587clear bands, shared bands of mutant L0420-3and YL002was328, while mutantQ1207-1and YL002was389, the polymorphic rate was53.08%and48.13%respectively.Among the48primer pairs,14polymorphic fragments of L0420-3and YL002were dectectby primer E4/M8,15polymorphic fragments of Q1207-1and YL002were dectect byprimer E5/M4, the number of fragments dectected by the other primer pairs was rangedfrom4to10, that showed the mutant was taken place evenly in the genome DNA. The Neisassociation coefficient of L0420-3and Q1207-1was0.6388and0.6831respectively, thisresult showed that genetic material of the two mutant has changed.