Actinomadura barringtoniae sp. Nov., an endophytic actinomycete isolated from the roots of Barringtonia acutangula (L.) Gaertn

A novel actinomycete strain, designated GKU 128^T, isolated from the roots of an Indian oak tree [Barringtonia acutangula (L.) Gaertn.] at Khao Khitchakut district, Chantaburi province, Thailand, was characterized by using a polyphasic approach. The strain formed a branched substrate and aerial mycelia which differentiated into straight to flexuous chains of smoothornamented spores. Analysis of the cell wall revealed the presence of meso-diaminopimelic acid and N-acetylmuramic acid in the peptidoglycan. The whole-cell sugars were glucose, madurose, mannose, rhamnose and ribose. Mycolic acids were absent. The major phospholipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol and phosphatidylinositolmannoside. The predominant menaquinones were MK-9(H₆), MK-9(H₈), MK-9(H₀) and MK-9(H₄). The major fatty acids were C_{16: 0}, C_{18: 1}ω9c and 10-methyl C_{18: 0} (tuberculostearic acid). The genomic DNA G+C content was 70.5 mol%. Based on 16S rRNA gene sequence analysis, strain GKU 128^T was closely related to the type strains of Actinomadura nitritigenes NBRC 15918^T (99.2% sequence similarity) and Actinomadura fibrosa JCM 9371^T (98.7 %). The levels of DNA–DNA relatedness between strain GKU 128^T and the closely related type species were less than 19 %. On the basis of phenotypic and genotypic characteristics, strain GKU 128^T could be distinguished from its closely related type strains and represents a novel species of the genus Actinomadura, for which the name Actinomadura barringtoniae sp. nov. (=TBRC 7225^T=NBRC 113074^T) is proposed.