| Abstract |
A novel actinomycete strain, JA03T, belonging to the genus Streptomyces, was isolated from the rhizosphere of Barringtonia racemosa (L.) Spreng. It was characterized taxonomically using a polyphasic approach. It grew at 25-37 °C, at pH 5-10 and with 6 % (w/v) NaCl. It contained ll-diaminopimelic acid in the cell-wall peptidoglycan. Ribose and glucose were detected in its whole-cell hydrolysate. The predominant cellular fatty acids were iso-C16 : 0, anteiso-C15 : 0, C16 : 0, iso-C14 : 0 and iso-C15 : 0. Detected polar lipids were phosphatidylethanolamine, diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol, phosphatidylinositol mannosides, unidentified phospholipids and unidentified amino lipids. Based on the results of 16S rRNA gene sequence analyses, strain JA03T showed highest similarity to Streptomyces filipinensis NBRC 12860T (98.76 %), Streptomyces fodineus TW1S1T (98.69 %) and Streptomyces shenzhennensis 172115T (98.68 %). Strain JA03T has a genome size of 9 092 851 bp with DNA G+C content of 71.28 mol%. The average nucleotide identity (ANI)-blast and ANI-MUMmer values of strain JA03T and related type strains were 79.6-89.2 and 86.7-92.5 %, respectively, and the digital DNA-DNA hybridization values were 27.3-46.4 %. Ethyl acetate extract of JA03T exhibited total phenolic content (33.4±0.6 µg mg-1 gallic acid equivalent), ferric reducing power value (70.8±1.8 µg mg-1 ascorbic acid equivalent) and 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity (IC50=67.0±21.1 µg ml-1). Intracellular reactive oxygen species and NO production in RAW264.7 macrophage cells induced by H2O2 and lipopolysaccharide were inhibited with IC50 of 67.40 and 16.95 µg ml-1, respectively. Based on the taxonomic results, it has been concluded that strain JA03T represents a novel species of the genus Streptomyces for which the name Streptomyces barringtoniae sp. nov., is proposed. The type strain is JA03T (=LMG 32415T=TISTR 2999T).
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