Comparative genomic analysis of the genus Novosphingobium and the description of two novel species Novosphingobium aerophilum sp. nov. and Novosphingobium jiangmenense sp. nov.

Members of the genus Novosphingobium are well known for their metabolically versatile and great application potential in pollution elimination. The three novel bacterial strains, designated 4Y4, 4Y9, and 1Y9A, were isolated from aquaculture water and characterized by using a polyphasic taxonomic approach. The 16S rRNA gene sequences phylogenetic analysis revealed that the three strains belonged to the genus Novosphingobium. The phylogenomic analysis indicated that the three strains formed two independent and robust branches distinct from all reference strains. The analyses of dDDH values and ANIs between the three strains and their relatives further demonstrated that the three strains represented two different novel genospecies. Comparative genomic analysis of the three isolates and 32 type strains of the genus Novosphingobium showed that the most important central metabolic pathways of these strains appeared to be similar, while specific and specialized metabolic pathways were flexible and variable among these strains. Chemotaxonomic characterization exhibited that the predominant cellular fatty acids were summed feature 8, summed feature 3, and C 2OH; the major polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidyldimethylethanolamine, phosphatidylglycerol, and sphingoglycolipid; the major respiratory quinone and polyamine were Q-10 and spermidine. The DNA G + C contents were 67.6 and 64.7 %. Based on the genotypic and phenotypic characteristics, strains 4Y4 and 1Y9A are concluded to represent two novel species of the genus Novosphingobium, for which the names Novosphingobium aerophilum sp. nov. (type strain 4Y4 = GDMCC 1.1828  = KACC 21946 ) and Novosphingobium jiangmenense sp. nov. (type strain 1Y9A = GDMCC 1.1936  = KACC 22085 ) are proposed.