Actinomycetospora aeridis sp. nov., Actinomycetospora flava sp. nov. and Actinomycetospora aurantiaca sp. nov., endophytic actinobacteria isolated from wild orchid (Aerides multiflora Roxb)

Three novel mycelium-forming actinobacteria, designated OC33-EN06^T, OC33-EN07^T, and OC33-EN08^T, were isolated from wild orchid (<i>Aerides multiflora</i> Roxb), collected from a hill evergreen forest in Northern Thailand. Strains OC33-EN06^T and OC33-EN07^T showed the highest 16S rRNA gene similarity with <i>Actinomycetospora lutea</i> TT00-04^T, 99.17 and 99.45%, respectively. Strain OC33-EN08^T showed high similarity with four species, namely '<i>Actinomycetospora termitidis</i> Odt1-22^T' (99.37%), <i>Actinomycetospora chiangmaiensis</i> DSM 45062^T (99.02%), <i>Actinomycetospora corticicola</i> 014-5^T (99.02%), and <i>Actinomycetospora soli</i> SF1^T (98.81%). Comparative genome analysis of OC33-EN06^T, OC33-EN07^T, and OC33-EN08^T with the closely related type strains showed that average nucleotide identity (ANI) based on blast, ANI based on MUMmer, and average amino acid identity values were less than 95% and the digital DNA-DNA hybridization values were less than 70%, all below the thresholds for species demarcation. The digital G+C content of OC33-EN06^T, OC33-EN07^T, and OC33-EN08^T were 74.5, 74, and 74 mol%, respectively. These three strains developed bud-like chains of non-motile cylindrical spores with a smooth surface. The cell-wall peptidoglycan contained <i>meso</i>-diaminopimelic acid. The whole-cell sugars contained ribose, arabinose, and galactose. The predominant menaquinone was MK-8(H₄). The phospholipid profile included phosphatidylcholine, phosphatidylethanolamine, phosphatidylmethylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, and phosphatidylinositol. Based on comparative analysis of genotypic, phenotypic and chemotaxonomic data, strains OC33-EN06^T (=TBRC 18349^T=NBRC 116543^T), OC33-EN07^T (=TBRC 18350^T=NBRC 116544^T), and OC33-EN08^T (=TBRC 18318^T=NBRC 116542^T) represent the type strains of three novel species of the genus <i>Actinomycetospora</i> for which the names <i>Actinomycetospora aeridis</i> sp. nov., <i>Actinomycetospora flava</i> sp. nov., and <i>Actinomycetospora aurantiaca</i> sp. nov., are proposed.