Streptomyces humi sp. nov., an actinobacterium isolated from soil of a mangrove forest

A novel Streptomyces strain, MUSC 119^T, was isolated from a soil collected from a mangrove forest. Cells of MUSC 119^T stained Gram-positive and formed light brownish grey aerial mycelium and grayish yellowish brown substrate mycelium on ISP 2 medium. A polyphasic approach was used to determine the taxonomic status of strain MUSC 119^T, which shows a range of phylogenetic and chemotaxonomic properties consistent with those of the genus Streptomyces. The cell wall peptidoglycan consisted of ll-diaminopimelic acid. The predominant menaquinones were identified as MK-9(H₈), MK-9(H₆) and MK-9(H₄). The polar lipid profile consisted of phosphatidylinositol, phosphatidylethanolamine, glycolipids, diphosphatidylglycerol and four phospholipids. The predominant cellular fatty acids were anteiso-C_15:0, iso-C_16:0, and anteiso-C_17:0. The cell wall sugars were glucose, mannose, ribose and rhamnose. The phylogenetic analysis based on 16S rRNA gene sequence similarity showed that strain MUSC119^T to be closely related to Streptomyces rhizophilus JR-41^T (99.0 % sequence similarity), S. panaciradicis 1MR-8^T (98.9 %), S. gramineus JR-43^T (98.8 %) and S. graminisoli JR-19^T (98.7 %). These results suggest that MUSC 119^T should be placed within the genus Streptomyces. DNA–DNA relatedness values between MUSC 119^T to closely related strains ranged from 14.5 ± 1.3 to 27.5 ± 0.7 %. The G+C content was determined to be 72.6 mol  %. The polyphasic study of MUSC 119^T showed that this strain represents a novel species, for which the name Streptomyces humi sp. nov. is proposed. The type strain of S. humi is MUSC 119^T (=DSM 42174^T = MCCC 1K00505^T).