Nocardioides candidus sp. nov. and Sphingomonas crocea sp. nov., isolated from soil of Inwang Mountain

Two novel strains, designated MH1 T and IW22 T , were isolated from soil of Inwang Mountain, Seoul, Republic of Korea. The nearly complete 16S rRNA gene sequences of strains MH1 T and IW22 T were 1,521 and 1,485 bp, respectively. Strain MH1 T showed the highest sequence similarity to Nocardioides pelophilus THG-T63 T (98.22%), Nocardioides stalactiti 1.0914 T (98.20%) and Nocardioides humilatus BN130099 T (98.02%). Strain IW22 T showed the highest similarity to Sphingomonas spermidinifaciens 9 NM-10 T (97.94%), Sphingomonas baiyangensis L-1–4 w-11 T (97.94%) and Sphingomonas yantingensis 1007 T (97.58%). Phylogenomic analysis based on 81 conserved core genes and average amino acid identity supported the placement of the two strains within the genera Nocardioides and Sphingomonas , respectively. The average nucleotide identity and digital DNA–DNA hybridization values between the novel strains and their closest relatives were below the species delineation thresholds. Comparative genomic analysis revealed the presence of distinct biosynthetic gene clusters, including terpene, polyketide and peptide-associated clusters, suggesting potential ecological adaptation to soil environments. The DNA G+C contents of strains MH1 T and IW22 T were 71.5 and 64.5 mol%, respectively. The major fatty acids of strain MH1 T were iso-C 16 : 0 and C 18 : 1 ω 9 c , whereas those of strain IW22 T were C 16 : 0 , C 18 : 1 ω 7 c and summed feature 3 (C 16 : 1 ω 6 c and/or C 16 : 1 ω 7 c ). Based on polyphasic taxonomic evidence, strains MH1 T and IW22 T represent novel species of the genera Nocardioides and Sphingomonas , respectively, for which the names Nocardioides candidus sp. nov. and Sphingomonas crocea sp. nov. are proposed.