Polyphasic Identification of Rhizomonospora bruguierae gen. nov., sp. nov., Isolated from Mangrove Rhizosphere Soil

A novel yellowish-white actinobacterial strain, designated as TS60-4C^T, was isolated from the rhizosphere soil of the mangrove Bruguiera gymnorhiza (L.) Lam. in Okinawa, Japan, and was subjected to a polyphasic assessment. The strain could grow at 0-3.0% NaCl concentrations (w/v), pH 6.0-10.0, and 20-37 °C. The 16S rRNA gene sequences-based phylogeny showed that the novel isolate belongs to the family Micromonosporaceae and that it shared the highest sequence similarity (98.4%) with Micromonospora craniellae LHW63014^T. The hydrolysate of cell-wall of strain TS60-4C^T contained alanine, glutamic acid, glycine, and meso-A2pm. The acyl type of muramic acid was N-glycolyl. The main (> 10%) fatty acids were anteiso-C_17:0 (22.1%), iso-C_16:0 (17.8%), iso-C_15:0 (14.7%), and anteiso-C_15:0 (10.3%) and the predominant menaquinones of the isolate were MK-9(H₆) and MK-9(H₄). The polar lipids of the isolate were phosphatidylethanolamine, diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol, an unidentified aminolipid, and three unidentified lipids. The genome size of strain TS60-4C^T was 6.7 Mbp with a DNA G + C content of 72.4%. The average nucleotide identity, digital DNA-DNA hybridization, and average amino acid identity value could differentiate strain TS60-4C^T from its closely related taxa. The genome of the strain had 22 putative biosynthetic gene clusters for secondary metabolites, indicating a significant potential as a producer of bioactive chemicals. Consequently, the strain is considered to represent a novel genus and a new species of the family Micromonosporaceae, for which the name Rhizomonospora bruguierae gen. nov., sp. nov. is proposed. The type species is R. bruguierae, with the type strain TS60-4C^T (= NBRC 107566^T = TBRC 2024^T).