Sphingomonas Immobilis sp. nov., and Sphingomonas natans sp. nov. bacteria isolated from soil

Two novel strains of bacteria, CA1-15(T) and BIUV-7(T), were isolated from soil samples gathered in Cheonan-si, Republic of Korea, and Inje-gun, Republic of Korea, respectively. These bacteria are Gram-negative, aerobic, and non-motile. Phylogenetic evaluations, using the sequence of the 16S rRNA gene, showed that strains CA1-15(T) and BIUV-7(T) belong to a distinctive clade within the family Sphingomonadaceae (order Sphingomonadales, class Alphaproteobacteria). The strains exhibited the highest similarity in their genetic makeup with representatives of the genus Sphingomonas. Strain CA1-15(T) was closely related to Sphingomonas echinoides NRRL B-3126(T) (97.8% similarity in 16S rRNA gene sequence), Sphingomonas oligophenolica JCM 12,082(T) (97.8%), Sphingomonas glacialis C16yT (97.6%) and Sphingomonas psychrolutea MDB1-A(T) (97.3%). Strain BIUV-7(T) was closely related to Sphingomonas nostoxanthinifaciens AK-PDB1-5(T) (97.0%), Sphingomonas vulcanisoli SN6-13(T) (96.3%), Sphingomonas naphthae DKC-5-1(T) (96.2%), and Sphingomonas prati W18RDT (95.7%). The optimal growth conditions for strains CA1-15(T) and BIUV-7(T) were determined to be at pH 7.0 and a temperature of 25 degrees C. Analysis of the cellular fatty acids of strain CA1-15(T) and BIUV-7(T) revealed that summed feature 8 (C18:1 omega 7c/C18:1 omega 6c) (60.4%), summed feature 8 (C18:1 omega 7c/C18:1 omega 6c) (62.9%) were the major component, respectively. Additionally, both strains exhibited ubiquinone Q-10 as their major respiratory quinone, and diphosphatidylglycerol (DPG), glycosphingolipid (SGL), and phosphatidylethanolamine (PE) as the major polar lipid. The genome of strain CA1-15(T) measures 4,133,944 bp, comprising 4,026 coding sequences (CDSs) and 46 tRNA genes. Similarly, the genome of strain BIUV-7(T) is 4,563,252 bp, characterized by 4,226 CDSs and 44 tRNA genes. The average nucleotide identity (ANI) analysis and digital DNA-DNA hybridization (dDDH) values between strain CA1-15(T) and other Sphingomonas species range from 73.2 to 79.9% and 19.4-22.9%, respectively. Comparatively, ANI and dDDH values between strain BIUV-7(T) and other Sphingomonas species are in the range of 72.9-76.5% and 19.3-20.9%, respectively. Based on the biochemical, chemotaxonomic, and phylogenetic analyses, it is evident that strains CA1-15(T) and BIUV-7(T) represent two novel bacterial species within the genus Sphingomonas. Accordingly, the names Sphingomonas immobilis sp. nov. and Sphingomonas natans sp. nov. are proposed. also, CA1-15(T)(= KCTC 92960(T) = NBRC 116547(T)) is the type strain of Sphingomonas immobilis and BIUV-7(T)(= KCTC 92961T = NBRC 116546(T)) is the type strain of Sphingomonas natans.