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

Abstract

Three novel mycelium-forming actinobacteria, designated OC33-EN06^T, OC33-EN07^T, and OC33-EN08^T, were isolated from wild orchid (Aerides multiflora 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 Actinomycetospora lutea TT00-04^T, 99.17 and 99.45%, respectively. Strain OC33-EN08^T showed high similarity with four species, namely 'Actinomycetospora termitidis Odt1-22^T' (99.37%), Actinomycetospora chiangmaiensis DSM 45062^T (99.02%), Actinomycetospora corticicola 014-5^T (99.02%), and Actinomycetospora soli 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 meso-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 Actinomycetospora for which the names Actinomycetospora aeridis sp. nov., Actinomycetospora flava sp. nov., and Actinomycetospora aurantiaca sp. nov., are proposed.