Description of Ornithinimicrobium cryptoxanthini sp. nov., a Novel Actinomycete Producing β-cryptoxanthin Isolated from the Tongtian River Sediments

Two novel Gram-stain-positive, aerobic, non-motile, and yellow-pigmented, irregular rod-shaped bacteria (JY.X269 and JY.X270^T) were isolated from the near-surface sediments of river in Qinghai Province, P. R. China (32°37'13″N, 96°05'37″E) in July 2019. Both strains were shown to grow at 15-35 °C and pH 7.0-10.0, and in the presence of 0-6.0% (w/v) NaCl. The 16S rRNA gene sequence analysis showed that the isolates were closely related to Ornithinimicrobium cavernae CFH 30183 ^T (98.6-98.8% 16S rRNA gene sequence similarity), O. ciconiae H23M54^T (98.5-98.6%) and O. murale 01-Gi-040^T (98.3-98.5%). The phylogenetic and phylogenomic trees based on the 16S rRNA gene and 537 core gene sequences, respectively, revealed that the two strains formed a distinct cluster with the above three species. The digital DNA-DNA hybridization (dDDH) and average nucleotide identity (ANI) values between our two isolates (JY.X269 and JY.X270^T) and other Ornithinimicrobium species were within the ranges of 19.0-23.9% and 70.8-80.4%, respectively, all below the respective recommended 70.0% and 95-96% cutoff point. Furthermore, the major cellular fatty acids (> 10.0%) of strains JY.X269 and JY.X270^T were iso-C_15:0, iso-C_16:0, and summed feature 9. Strain JY.X270^T contained MK-8(H₄) and ornithine as the predominant menaquinone and diagnostic diamino acid component within the cell wall teichoic acids. β-cryptoxanthin (C₄₀H₅₆O) can be extracted from strain JY.X270^T, and its content is 6.3 µg/ml. Based on results from the phylogenetic, chemotaxonomic, and phenotypic analyses, the two strains could be classified as a novel species of the genus Ornithinimicrobium, for which the name Ornithinimicrobium cryptoxanthini sp. nov. is proposed (type strain JY.X270^T = CGMCC 1.19147^T = JCM 34882^T).