Endophytic Sphingomonas Hylomeconis Sp. Nov., Isolated From The Stem Of Hylomecon Japonica

In this study, 90 endophytic bacteria were isolated from 5 traditional medicinal herbs collected from Taibai Mountain in Shaanxi Province, north-west China. 16 S r RNA gene sequence analysis revealed a high phylogenetic diversity with 39 taxa at the genus level, which were spread across the phyla Actinobacteria, Bacteroidetes, Firmicutes and Proteobacteria. Isolates belonging to the genera Pseudomonas and Rhizobium were the most predominant. Seven phytopathogenic fungi and four bacteria were used as indicator organisms to determine the antimicrobial activities of the 90 endophytes and 15 bacterial isolates showed significant antimicrobial activity against at least five of the test strains. The biosynthetic potential of all 90 isolates was further investigated by the detection of putative type I polyketide synthase(PKS) and nonribosomal peptide synthetase(NRPS) genes. Sequence analysis confirmed that 11 isolates were positive for PKS genes and 7 isolates for NRPS genes. The obtained nucleotide sequence data were deposited in the Gen Bank nucleotide sequence database under accession numbers KF539768 to KF539778 for PKS genes and KF539779 to KF539785 for NRPS genes.A yellow-pigmented bacterium, designated strain GZJT-2T, was isolated from the stem of Hylomecon japonica(Thunb.) Prantl et Kündig collected from Taibai Mountain in Shaanxi Province, north-west China. Cells of strain GZJT-2T were Gram-reaction-negative, strictly aerobic, rod-shaped, non-spore-forming and non-motile. Phylogenetic analyses based on 16 S r RNA gene sequences showed that strain GZJT-2T was a member of the genus Sphingomonas, with sequence similarities of 92.1–96.9 % to type strains of recognized Sphingomonas species(92.1 % to S. oligoaromativorans SY-6T and 96.9 % to S. oligophenolica JCM 12082T). Strain GZJT-2T contained ubiquinone-10(Q-10) as the predominant respiratory quinone and symhomospermidine as the major polyamine. The major cellular fatty acids were summed feature 8(comprising C18:1ω7c and/or C18:1ω6c), summed feature 3(comprising C16:1ω7c and/or C16:1ω6c), C16:0 and C14:0 2-OH. Phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylmonomethylethanolamine, phosphatidylcholine, sphingoglycolipid, four unidentified phospholipids, an unidentified aminolipid and four unidentified lipids were detected in the polar lipid profile. The DNA G+C content was 62.5± 0.3 mol%. Based on data from the phenotypic, phylogenetic and DNA–DNA relatedness studies, strain GZJT-2T is considered to represent a novel species of the genus Sphingomonas, for which the name Sphingomonas hylomeconis sp. nov. is proposed. The type strain is GZJT-2T(=CCTCC AB 2013304 T = KCTC 42739T).In summary, the survey of five wild medicinal plants have revealed an unexpected diversity of endophytic bacteria, some of which have been found to display broad-spectrum antimicrobial activity. Furthermore, sixteen isolates contained detectable PKS and/or NRPS genes. For the isolates which displayed significant antimicrobial activity in the present study, further research is needed to elucidate the chemical constituents of the antimicrobial metabolites and their biosynthetic pathways. In addition, a recognized novel species of the genus Sphingomonas was identified, suggest that the traditional medicinal plants of Taibai Mountain represent a rich reservoir for the isolation of diverse endophytic bacteria that include rare and novel species.