Phytohabitans aurantiacus sp. nov., an actinomycete isolated from soil.

A novel actinomycete, designated RD004123T, was isolated from a soil sample collected in Hokkaido, Japan, and its taxonomic position was investigated by a polyphasic approach. Phylogenetic analysis based on 16S rRNA gene sequence comparisons revealed that strain RD004123T fell within the cluster of the family Micromonosporaceae but did not form a reliable cluster with any member of the family. The similarity values between strain RD004123T and the type species of 29 genera in the family Micromonosporaceae were 91.7-97.7 %. Meanwhile, phylogenomic analyses indicated that strain RD004123T was closely related to members of the genus Phytohabitans. Strain RD004123T contained both meso-diaminopimelic acid and l-lysine as the diagnostic diamino acids of the peptidoglycan. The predominant isoprenoid quinones were MK-10(H8) and MK-10(H6), and the major fatty acids were anteiso-C17 :  0, iso-C16 :  0, iso-C15 :  0 and C17 :  0. The detected polar lipids were phosphatidylinositol mannosides, phosphatidylinositol, phosphatidylethanolamine and diphosphatidylglycerol. These chemotaxonomic features corresponded to those of the genus Phytohabitans. Meanwhile, the results of genome comparison analyses and phenotypic characterizations distinguished strain RD004123T from the other members of the genus Phytohabitans. Therefore, strain RD004123T should be assigned as representing a novel species of the genus Phytohabitans, for which the name Phytohabitans aurantiacus sp. nov. is proposed. The type strain is RD004123T (=NBRC 114997T=DSM 114330T).

Phytohabitols A-C, δ-Lactone-Terminated Polyketides from an Actinomycete of the Genus Phytohabitans.

Phytohabitols A-C (1-3), new terminally δ-lactonized linear polyketides, were isolated from the culture extract of a rare actinomycete of the genus Phytohabitans. The structures of 1-3, substituted with multiple methyl and hydroxy groups on a conjugated and a skipped diene-containing backbone, were elucidated by NMR and MS spectroscopic analyses. The absolute configuration of 1 was determined by chemical derivatization and chiral anisotropic analysis, coupled with ROESY and J-based configuration analysis. In addition, closely similar 1H and 13C NMR data and optical rotations among 1-3 supported the same stereochemistry of these polyketides. The related streptomycetes metabolites lagunapyrones B, C, and D have α-pyrone rings on the linear part in place of the δ-lactone, but their chirality at the C19-C21 stereocenters were opposite from those described here, posing a question on the previous assignment made solely by comparison of the optical rotations of four possible diastereomers. Compounds 1-3 inhibited migration of cancer cells with IC50 values of 15, 11, and 8.3 µM, respectively, at noncytotoxic concentrations. In addition, 1-3 displayed potent antitrypanosomal activity against Trypanosoma cruzi with IC50 values of 12, 6.4, and 18 µM, comparable to a commonly used therapeutic drug, benznidazole (IC50 16 µM).