Sphingomonas rustica sp. nov. and Sphingomonas agrestis sp. nov., novel carotenoid-producing bacterial species isolated from farm soil

Two yellow-pigmented novel strains, designated HF-S3^T and HF-S4^T, were isolated from farm soil in Paju, Republic of Korea. Cells of the two strains are characteristically Gram-stain-negative, facultatively anaerobic, catalase-and oxidase-positive, non-motile and rod-shaped. Strain HF-S3^T grew at 10–37 °C, while HF-S4^T grew at 15–35 °C. Both strains grew at pH 5.0–12.0 and in NaCl concentrations (w/v) of 0–2.0%. Phylogenetic analysis based on 16S rRNA gene sequences indicated that HF-S3^T and HF-S4^T belong to the genus Sphingomonas, with HF-S3^T exhibiting 97.7, 97.6 and 97.4% similarity to Sphingomonas cannabina DM2-R-LB4^T, Sphingomonas leidyi DSM 4733^T and Sphingomonas canadensis FWC47^T, respectively. Strain HF-S4^T displayed 97.9, 97.7 and 97.6% similarity to Sphingomonas psychrotolerans Cra20^T, Sphingomonas gei ZFGT-11^T and Sphingomonas naasensis KIS18-15^T, respectively. The DNA G+C contents of HF-S3^T and HF-S4^T were 67.0 and 66.5 mol%, respectively. The digital DNA– DNA hybridization and average nucleotide identity values among the novel and related type strains were 20.2–28.2% and 75.9– 84.3%, respectively. They all contained C_14:0 2-OH and C_16:0, summed feature 8 (C_18:1 ω6c and/or C_18:1 ω7c) as the major fatty acids and ubiquinone-10 as the predominant respiratory quinone. Strains HF-S3^T and HF-S4^T were found to produce carotenoid-type pigments. Based on polyphasic taxonomic analysis, the new isolates ostensibly represent two novel species of the genus Sphin-gomonas, with the proposed names Sphingomonas rustica sp. nov. and Sphingomonas agrestis sp. nov. for strains HF-S3^T and HF-S4^T, respectively. The S. rustica and S. agrestis type strains are HF-S3^T (=KACC 23554^T =TBRC 18352^T) and HF-S4^T (=KACC 23386^T =TBRC 17899^T), respectively.