Description of Ornithinimicrobium pulveris sp. nov. and Ornithinimicrobium carbonis sp. nov., isolated from a coal mine working environment.

Four actinobacterial strains, Y1847ᵀ, Y1694, W1665ᵀ and W1679, were isolated from the coal mine working environment in Shanxi Province, China. Sequence comparison of 16S rRNA genes indicated that the strains were closely related to Ornithinimicrobium kibberense K22-20ᵀ, with similarities ranging from 98.06 to 98.47%. Further phylogenetic analyses (based on 16S rRNA gene and core-genome) placed the strains within the genus Ornithinimicrobium and formed two distinct clades. The strains are Gram-stain-positive, facultative anaerobes and non-motile. Specifically, strain Y1847ᵀ is coccoid, whereas strain W1665ᵀ is rod-shaped. Their cell-wall peptidoglycan contains ornithine but lacks serine, with menaquinone MK-8(H4) as the predominant respiratory quinone and diphosphatidylglycerol and phosphatidylglycerol as the major polar lipids. The strains differed in their major fatty acid profiles: Y1847ᵀ and Y1694 contained iso-C15:0, iso-C16:0 and summed feature 9 (comprising 10-methyl C16:0 and/or iso-C17:1  ω9c), whereas W1665ᵀ and W1679 contained iso-C15:0, iso-C17:0 and summed feature 9. Based on phylogenetic, phenotypic and chemotaxonomic analyses, strains Y1847ᵀ/Y1694 and W1665ᵀ/W1679 represent two novel species within the genus Ornithinimicrobium, for which the names Ornithinimicrobium pulveris sp. nov. (type strain Y1847ᵀ=KCTC 59532ᵀ=GDMCC 1.5550ᵀ) and Ornithinimicrobium carbonis sp. nov. (type strain W1665ᵀ=KCTC 59593ᵀ=GDMCC 1.5709ᵀ) are proposed.