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 Sphingomonas, 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.