Labedaea rhizosphaerae gen. nov., sp. nov., isolated from rhizosphere soil

Abstract

A novel actinomycete, designated strain RS-49(T), was isolated from the rhizosphere soil of a cliff-associated plant (Peucedanum japonicum Thunb.) in the Republic of Korea and subjected to a polyphasic taxonomic study. The results of comparative 16S rRNA gene sequence analyses showed that the organism belonged to the family Pseudonocardiaceae, suborder Pseudonocardineae and that it was most closely related to members of the genera Kibdelosporangium (96.6-97.0% sequence similarity), Actinokineospora (96.3-96.7%), Streptoalloteichus (96.2%) and Actinophytocola (96.2%). Substrate mycelia were well-developed and whitish or pale yellow to strong yellow. Aerial mycelia were branched and fragmented into rod-shaped elements. Single spherical spores were produced directly on the substrate mycelium. Sporangium-like structures and fragmentation of the substrate mycelium were absent. The diagnostic diamino acid in the cell-wall peptidoglycan was meso-diaminopimelic acid. The acyl type of the muramic acid residues in the peptidoglycan was N-acetylated. Whole-cell sugars were glucose, rhamnose, galactose, ribose, mannose, arabinose and xylose. The major menaquinone was MK-9(H(4)). Small amounts of MK-8 and MK-9(H(2)) were also detected. The polar lipids contained diphosphatidylglycerol, phosphatidyldimethylethanolamine, phosphatidylglycerol, phosphatidylinositol, an unknown phospholipid and an unknown lipid. The predominant fatty acids were iso-C(15:0) and iso-C(16:0). The DNA G+C content was 64.2 mol%. The phenotypic and phylogenetic characteristics show that strain RS-49(T) can be differentiated from members of all genera in the suborder Pseudonocardineae and thus represents a novel species in a new genus for which the name Labedaea rhizosphaerae gen. nov., sp. nov. is proposed; the type strain of the type species is RS-49(T) ( = KCTC 19662(T) = DSM 45361(T)).