Isolation and characterization of Novosphingobium oxfordense sp. nov. and Novosphingobium mississippiense sp. nov. from soil, with LC-MS/MS and genome-based investigation of their glycosphingolipid production

Members of the genus Novosphingobium are well known for the biosynthesis of glycosphingolipids. Here, we are reporting two recently discovered species belonging to this genus, which were isolated from a potted tomato plant in Oxford, Mississippi, USA. The cells of both strains grew aerobically, were rod-shaped, and formed yellow colonies. According to the 16S rRNA gene and whole genome-based phylogeny, both strains have the highest similarity to N. clariflavum 164 T . Genomes of both strains had a G + C content of 64 mol %, and assemblies with four circular contigs: two plasmids and two larger sequences over a megabase long. The analysis of the ortho Average Nucleotide Identity scores, along with digital DNA-DNA hybridization values, demonstrated that the two strains are distinct and unique species. Comparative genomic analysis with the reference strains of the genus Novosphingobium showed that the central metabolic pathways of these strains appeared to be similar, with slight variation consistent with prior reports of strains within the genus. Using MS/MS fragmentation data, glycosphingolipids with a hexuronic acid head-group could be annotated. A Sequence Similarity Network of the glycosyltransferase genes within these organisms showed a homolog of the known bacterial gene responsible for adding glucuronic acid to ceramide, consistent with the MS/MS analysis. These strains' major isoprenoid quinone was Q-10, and their predominant polyamine was spermidine. The phenotypic, chemotaxonomic, and genotypic features of strains BL-8A and BL-8H lead to the conclusion that these are two novel species of the genus Novosphingobium , for which the names Novosphingobium oxfordense (type strain = BL-8A T = NRRL B-65725 T = LMG 34032 T = ATCC TSD-464 T ) and Novosphingobium mississippiense (type strain = BL-8H T = NRRL B-65726 T = LMG 34033 T = ATCC TSD-465 T ) are proposed.