Actinokineospora lacus sp. nov., an actinomycete isolated from the lakeside soil of Xinsheng Lake in Qinghai Province.

A novel Gram-positive aerobic actinomycete, Actinokineospora lacus 24-640ᵀ, was isolated from the lakeside soil of Xinsheng Lake in Qinghai Province, PR China. The strain produced pale-yellow substrate mycelium, light orange aerial mycelium and pale-yellow pigment on ISP 2 medium. Aerial mycelia appeared as elongated, chain-like structures with irregular branching and non-motile cylindrical spores with wrinkled surfaces. The strain grew between 15 and 30 °C, NaCl concentrations of 0-3% and pH 6-8. Its cell wall peptidoglycan contained meso-diaminopimelic acid, and the whole-cell sugars were ribose, arabinose, glucose and galactose. The major menaquinones were MK-9(H₄) and MK-10(H₄). The polar lipid profile consisted of diphosphatidylglycerol, phosphatidylinositol, phosphatidylethanolamine, phosphatidylethanolamine with hydroxy fatty acids, phosphatidylinositol mannosides, an unidentified glycolipid and an unidentified phospholipid. The predominant fatty acids (≥10.0%) were iso-C16:0, iso H-C16:1 and C17:1  ω6c. The draft genome was 7.6 Mb with a DNA G+C content of 72.1 mol%. Full-length 16S rRNA gene sequence analysis revealed that A. lacus 24-640T belongs to the genus Actinokineospora, showing the highest sequence identity to Actinokineospora guangxiensis CGMCC 4.7154T (97.3%) and clustering with Actinokineospora fastidiosa IMSNU 20054T in 16S rRNA gene phylogenetic trees. However, whole-genome comparisons were well below the accepted species delineation thresholds: ANIb/ANIm values of 81.5%/86.4% to A. fastidiosa and 80.0%/85.8% to A. guangxiensis and corresponding digital DNA-DNA hybridization values of 27.0 and 24.3%, respectively. The phylogenomic tree indicated that A. lacus 24-640T formed an independent subclade. Furthermore, phenotypic, chemotaxonomic characteristics and genomic analyses confirmed that A. lacus 24-640ᵀ differs significantly from its closest relatives, A. fastidiosa IMSNU 20054ᵀ and A. guangxiensis CGMCC 4.7154ᵀ. In addition, A. lacus 24-640T exhibited a high 16S rRNA gene sequence similarity (97.01%) to Actinokineospora acnipugnans R434T; however, it could be distinguished from A. acnipugnans R434T based on phylogenetic analysis, phenotypic characteristics and chemotaxonomic features. Therefore, A. lacus 24-640T represents a novel Actinokineospora species, for which the name Actinokineospora lacus sp. nov. is proposed; the type strain is 24-640T (=MCCC 1K09702T=KCTC 59492T).