Identification And Efficiency Of A Novel Bio-Control Isolate OH11

Totally 1056 bacterial isolates were isolated from different plant rhizosphere soils, 7 isolates of which showed antibiosis activity to plant pathogens, such as Phytophthora capsid, Pythium aphanidermatum, Rhizopus stolonifer, Sclerotinia sclerotiorum, Rhizoctonia solani, Fusarium oxysporium f. sp. vasinfectum, Fusarium solani, Verticillium dahliae, Ralstonia solanacearum and Xanthomonas campestris pv. Campestris, Xanthomonas oryzae pv. oryzae, Xanthomonas oryzae pv. oryzicola, Clavibacter michiganense. Based on the phenotypic characteristics and analysis of the 16S rDNA fragment, BOH3 was identified as Pseudomonas fluorescens and BOH2, BOH5, BOH46, BOH108, BOH116 were 5 distinct Bacillus spp., OH11 was a novel antagonist isolate which had not been reported in China.Isolate OH11 was originated from vegetable soil in Nanjing, China. It was a kind of gram-negative rod bacterium lacking flagella. Oberserved by transmission electron microscope, flexible rods were 0.4 by 1 to 6μm and the lengths were variable along with age. On TSA, color of strain colony was pale yellow to brown yellow, transparent or translucent, a soluble brownish black pigment was produced cumulating with age. Colony was circular to irregular with a entire or erose edge where thin edges with apparent tracks or trails could be seen spreading from the colony centre, which was indicative of gliding motility. It was moderate mucosity in liquid medium. It could grow between 5-35℃ with the optimum growth temperature of 28-30℃.Biolog physiological and biochemical test indicated that D-cellobiose, a-D-lactose and sucrose could be metabolized more efficiently than type strain (Lysobacter enzymogenes ATCC29487) . It had esterases activity which could degrade Tween-20 as well as proteases and chitinases activities. It could degradate carboxymethyl cellulose and gelation rather than starch and cellulose. citrate could be used as a sole carbon source but urea was not used as a sole nitrogen source. It was inhibited by 0.1% sodium lauryl sulfate. It showed high levels of resistance against penicillin, rifampin, ampicillin, streptomycin, kanamycin and tetracycline, except chloramphenicol. It had β-hemolysis and grew well on both MacConkey and EMB plates. The G+C content for isolate OH11 was 69.8 mol%.