Isolation Of Against Some Phytopathogenic Fungi Actinomyces And Identification Of A Novel Actinomyce

This research aimed at screening of antagonistic actinomycetes with great activity to plant pathogens, identifying the antagonistic strain and studying the actinomycetes substances produced by them preliminarily to searching for the source of new agri-antibiotics.In this experiment, a total 37 actimycetes were isolated from longan and linden rhizosphere mud collected from Nanshan Temple of Guangxi Province. The antibacterial activity was determined by plate method, and the inhibition zone diameter of 11 strains were above 15mm. Alernaria solani, Rhizoctonia solani, Fusarium oxysporum, Corynespora cassiicola and Sclerotinia sclerotiorum were treated as bioassay-guided. Eleven strains showed activity against at least one of the five phytopathogenic fungi, six strains showed strains showed activity against three or more fungi, which were L9,P1,P6,P9,P12,P13, respectively. The strain L9 showed activity against all of the five phytopathogenic fungi, and the inhibition zone diameter of 11 strains were above 15mm.As part of a program to discover potential actinomycetes as novel antibiotic producers, an aerobic actinomycete strain P23 was isolated. Due to phenotypic character of the strain P23, the taxonomic identification was carried out. The isolate was Gram-positive, aerobic actinomycete, and formed branching, non-fragmenting vegetative hyphae and produced black pigment on Yeast /malt extract (ISP medium 2). The G+C content of the DNA was 76.6 mol%. The organism was closely related to the type strains of A. cyanogriseus, A. spitiensis and A. hymeniacidonis, currently the only three Actinoalloteichus species with validly published names, sharing 16S rRNA gene similarities with these strains of 96.4, 96.6 and 98.1 %, respectively. However, sequence similarities to all other species of related genera with validly published names were lower than 95 %. The DNA-DNA hybridization revealed 46.8 % relatedness between strain P23 and the type strain of A. hymeniacidonis, which is well below the 70 % value, which is considered to be the threshold for the delineation of genomic species. The organism had chemotaxonomic characteristics typical of the genus Actinoalloteichus: meso-A2pm as the cell wall amino acid (cell wall type III), iso- and anteiso-branched fatty acids as the predominant cellular fatty acids and MK-9(H4) as the major menaquinone. However, the quantity of MK-10(H4) and 18:0 saturated fatty acid in this strain was more than other species, and 17:0 cyclopropane acid was only present in the strain.In conclusion, it is evident from the genotypic, chemotaxonomic and phenotypic data that strain P23 should be classified as a representative of a novel species of the genus Actinoalloteichus, for which the name Actinoalloteichus guangxiensis sp. nov. is proposed (=CGMCC 4.5714T =NBRC 106685T)...