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 <i>Sphingomonas</i>, with HF-S3^T exhibiting 97.7, 97.6 and 97.4% similarity to <i>Sphingomonas cannabina</i> DM2-R-LB4^T, <i>Sphingomonas leidyi</i> DSM 4733^T and <i>Sphingomonas canadensis</i> FWC47^T, respectively. Strain HF-S4^T displayed 97.9, 97.7 and 97.6% similarity to <i>Sphingomonas psychrotolerans</i> Cra20^T, <i>Sphingomonas gei</i> ZFGT-11^T and <i>Sphingomonas naasensis</i> 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 <i>ω</i>6<i>c</i> and/or C_18:1 <i>ω</i>7<i>c</i>) 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 <i>Sphingomonas</i>, with the proposed names <i>Sphingomonas rustica</i> sp. nov. and <i>Sphingomonas agrestis</i> sp. nov. for strains HF-S3^T and HF-S4^T, respectively. The <i>S. rustica</i> and <i>S. agrestis</i> type strains are HF-S3^T (=KACC 23554^T =TBRC 18352^T) and HF-S4^T (=KACC 23386^T =TBRC 17899^T), respectively.