Rhizocola hellebori gen. nov., sp. nov., an actinomycete of the family Micromonosporaceae containing 3, 4-dihydroxydiaminopimelic acid in the cell-wall peptidoglycan

An actinomycete strain, K12-0602^T, was isolated from the root of a Helleborus orientalis plant in Japan. The 16S rRNA gene sequence of strain K12-0602^Tshowed that it had a close relationship with members of the family Micromonosporaceae and the 16S rRNA gene sequence similarity values between strain K12-0602^T and type strains of type species of 27 genera belonging to the family Micromonosporaceae were below 96.2 %. MK-9 (H₄) and MK-9 (H₆) were detected as major menaquinones, and galactose, xylose, mannose and ribose were present in the whole-cell hydrolysate. The acyl type of the peptidoglycan was glycolyl. Major fatty acids were iso-C_{15: 0}, iso-C_{16: 0}, C_{17: 1}ω9c and anteiso-C_{17: 0}. Phosphatidylethanolamine was detected as the phospholipid corresponding to phospholipid type II. The G+C content of the genomic DNA was 67 mol%. Analyses of the cell-wall peptidoglycan by TLC and LC/MS showed that it was composed of alanine, glycine, hydroxylglutamic acid and an unknown amino acid, which was subsequently determined to be 3, 4-dihydroxydiaminopimelic acid using instrumental analyses, including NMR and mass spectrometry. On the basis of the phylogenetic analysis and chemotaxonomic characteristics, strain K12-0602^T represents a novel species of a new genus in the family Micromonosporaceae, for which the name Rhizocola hellebori gen. nov., sp. nov. is proposed. The type strain of the type species is K12-0602^T (= NBRC 109834^T = DSM 45988^T). This is the first report, to our knowledge, of 3, 4-dihydroxydiaminopimelic acid being found as a diamino acid in bacterial cell-wall peptidoglycan.