The taxonomic status of a bacterium designated strain IMMIB SR-4(T) isolated from an oil-contaminated soil sample was characterized by using a polyphasic approach. Chemotaxonomic investigations revealed the presence of cell-wall chemotype IV, short-chain mycolic acids that co-migrated with those extracted from members of the genus Williamsia and that on pyrolysis GC produce C(16:0) and C(18:0) fatty acids, and dihydrogenated menaquinone with nine isoprene units as the predominant menaquinone. The generic assignment was confirmed by 16S rRNA gene sequence analysis. Comparative analysis of the 16S rRNA gene sequence showed that strain IMMIB SR-4(T) formed a distinct phyletic line within the genus Williamsia, displaying sequence similarities of 95.5-98.1 % with the type strains of recognized Williamsia species. Strain IMMIB SR-4(T) was distinguished from the type strains of recognized species of the genus Williamsia based on a set of phenotypic features. The genotypic and phenotypic data indicated that strain IMMIB SR-4T represents a novel species of the genus Williamsia, for which the name Williamsia serinedens sp. nov. is proposed. The type strain is IMMIB SR-4(T) (=DSM 45037(T) = CCUG 53151(T))
