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(T) showed 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 (H-4) and MK-9 (H-6) 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-17:10 omega 9c 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-dihydroqdiaminopimelic acid being found as a diamino acid in bacterial cell-wall peptidoglycan.