Isolation, Screening, Identification And Inhibitory Effect Of Bacillus From Qinling Mountain Soil

Being the important boundary of the North and South of China as well as thewatershed of the Yellow River and Yangtze River, Mountain Qin promises greatresearch values and potentials with it being heavily wooded, abundant in vegetation,rich in soil organic compounds, and special in predominant microorganisms. Bacillushas endospore, strong adversity resistance，rapid growth, and requires relative simplenutritious components from environment to successfully colonize around roots, all ofwhich earn for it has high reputation in the biological control of plant diseases. In thisstudy, we collected soil samples from Taibai distract of Mountain Qin and attemptedto isolate Bacillus that can contain numerous plant diseases, after identification andoptimizing the fermentation conditions for them, we investigate their antibacterialmetabolites. The ultimate goal of this study is to find new resources for microbialpesticides.From23soil samples,467strains of Bacillus were isolated using the traditionalmicroorganism isolation methods. Ten fungi including Pyricularia oryzae, Botrytiscirerea, Cytospora sp., Venturia pirina, Fusarium graminearum, Setosphaeriaturcica, Physalospora piricola and so on were used as plant pathogens to test theresistance ability of the isolated541strains with slide cultivation method, amongwhich nine strains showed interested features. Fermentation broth filtrate rescreeningand single spore resistance ability screening eventually identified one optimum,An-ctc-y-1, from the nine screened strains. Specially, An-ctc-y-1mostly retarded thegrowth of Pyricularia oryzae and Botrytis cirerea, mold with the respectivesuppressing rates as93.50%and92.60. Combined with related papers, the evidencefrom the cultural performances, morphological characteristics, physiological andbiochemical features and the sequencing and analysis of its16S rRNA of An-ctc-y-1strain，we initially define An-ctc-y-1is Bacillus methylotrophicus.Fermentation condition optimization was carried out using single factor andorthogonal tests. The results showed that the basic culture medium for An-ctc-y-1is LB, and it grows well with initial pH was7.5, cultivation temperature was32℃, rotate speed was150r/min, and fermentation time was48h.The An-ctc-y-1strain shows high resistance against a large spectrum ofpathogens, with the inhibitory rate of Pyricularia oryzae, Botrytis cirerea, Venturiapirina, Phytophthora capsici and Physalospora piricola all above90%.Theinvestigation into antimicrobial metabolites of metabolisms indicates that thecontained fungi showed retarded hypha growth with some of them contorted, swollen,distorted or tumescent in tips, and condensed protoplasm, which distributes unevenlyand sometime breaks up. In addition, the metabolism of An-ctc-y-1can not onlycontain spore germination but make spores abnormal.Through the assay which the preventive and therapeutic function against plantpathogens in greenhouse of metabolites of An-ctc-y-1strain, we found that it may bebetter used for the treatment against Botrytis cirerea and Tomato phytophthora rot.Moreover, the fermentation liquid can improve the germination rates of the seeds oftomato, cucumber, and so forth, it also has the function of promoted growth whichrequires further study.