Abstract
The taxonomic positions of two novel aerobic, Gram-positive actinobacteria, designated strains RB29(T) and RB68(T), were determined using a polyphasic approach. Based on 16S rRNA gene sequence analysis, the closest phylogenetic neighbours of RB29(T) were identified as Actinomadura rayongensis DSM 102126(T) (99.2 % similarity) and Actinomadura atramentaria DSM 43919(T) (98.7 %), and for strain RB68(T) was Actinomadura hibisca DSM 44148(T) (98.3 %). Digital DNA-DNA hybridization (dDDH) between RB29(T) and its closest phylogenetic neighbours, A. rayongensis DSM 102126(T) and A. atramentaria DSM 43919(T), resulted in similarity values of 53.2 % (50.6-55.9 %) and 26.4 % (24.1-28.9 %), respectively. Additionally, the average nucleotide identity (ANI) was 93.2 % (94.0 %) for A. rayongensis DSM 102126(T) and 82.3 % (78.9 %) for A. atramentaria DSM 43919(T). dDDH analysis between strain RB68(T) and A. hibisca DSM 44148(T) gave a similarity value of 24.5 % (22.2-27.0 %). Both strains, RB29(T) and RB68(T), revealed morphological characteristics and chemotaxonomic features typical for the genus Actinomadura, such as the presence of meso-diaminopimelic acid in the cell wall, galactose and glucose as major sugar components within whole-cell hydrolysates and the absence of mycolic acids. The major phospholipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol and phosphatidylinositol mannoside. Predominant menaquinones were MK-9(H(6)) and MK-9(H(8)) for RB29(T) and MK-9(H(4)) and MK-9(H(6)) for RB68(T). The main fatty acids were identified as 10-methyloctadecanoic acid (10-methyl C(18:0)), 14-methylpentadecanoic acid (iso-C(16:0)), hexadecanoic acid (C(16:0)) and cis-9-octadecanoic acid (C(18 : 1) ω9c). Here, we propose two novel species of the genus Actinomadura: Actinomadura rubteroloni sp. nov. with the type strain RB29(T) (=CCUG 72668(T)=NRRL B-65537(T)) and Actinomadura macrotermitis sp. nov. with the type strain RB68(T) (=CCUG 72669(T)=NRRL B-65538(T)).