Novosphingobium panipatense sp. nov. and Novosphingobium mathurense sp. nov., from oil-contaminated soil.

In an ongoing attempt to analyse the diversity of culturable micro-organisms from oil-contaminated soil, two yellow-pigmented, Gram-negative, halophilic bacterial strains (SM16T and SM117T) were isolated. These two strains were characterized using a polyphasic approach. Strains SM16T and SM117T showed a range of phenotypic and chemotaxonomic properties that were consistent with those of members of the genus Novosphingobium. Both strains contained sphingoglycolipids, thus confirming that they belong to the Alphaproteobacteria. Furthermore, the polar lipid profile consisted of phosphatidylglycerol, phosphatidyldimethylethanolamine and phosphatidylethanolamine, with minor amounts of phosphatidyldimethylethanolamine, phosphatidylcholine and phosphatidylmonomethylethanolamine. Spermidine was the major polyamine in the cell wall, a characteristic feature of members of the genus Novosphingobium. Fatty acid analysis revealed the presence of C(18 : 1)omega7c, C(16 : 0) and C(14 : 0) 2-OH in both isolates, a characteristic feature of sphingomonads. 16S rRNA gene sequence similarities with the type strains of the most closely related species of the genus Novosphingobium (Novosphingobium pentaromativorans and Novosphingobium resinovorum) were less than 98.8 % for both strains. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strains SM16T and SM117T fall in the clade represented by the genus Novosphingobium. Strains SM16T and SM117T shared 98.8 % similarity in their 16S rRNA gene sequences and their mean level of DNA-DNA relatedness was 8.5 %. Strains SM16T and SM117T differed from each other with respect to their morphological, physiological and chemotaxonomic properties. Thus, these results indicate that strains SM16T and SM117T belong to separate species of the genus Novosphingobium, for which the names Novosphingobium panipatense sp. nov. and Novosphingobium mathurense sp. nov. are proposed; the type strains are SM16T (=CCM 7472T =MTCC9019T) and SM117T (=CCM 7473T =MTCC9020T), respectively.