Sphingobacterium lactis sp. nov. and Sphingobacterium alimentarium sp. nov., isolated from raw milk and a dairy environment

Abstract

Four non-fermenting, rod-shaped, Gram-staining-negative bacterial strains, designated WCC 4512(T), WS 4555, WCC 4521(T) and WS 4556, were isolated from raw milk and the dairy environment. Phylogenetic analyses based on 16S rRNA and groEL gene sequences demonstrated the affiliation of the four strains to two distinct clusters within the class Sphingobacteriia, phylum 'Bacteroidetes'. Strains WCC 4512(T) and WS 4555 showed the highest 16S rRNA gene sequence similarity to the type strain of S. daejeonense (97.3 and 97.2%, respectively), whereas strains WCC 4521(T) and WS 4556 were most closely related to S. composti LMG 23401(T) (97.6% 16S rRNA gene sequence similarity). The DNA G+C contents of strains WCC 4512(T) and WCC 4521(T) were 44.2 and 39.3 mol%, respectively. The major cellular fatty acids and the presence of menaquinone MK-7 as the predominant quinone for both strains WCC 4512(T) and WCC 4521(T) supported their affiliation to the genus Sphingobacterium. DNA-DNA hybridization experiments between strain WCC 4512(T) and S. daejeonense LMG 23402(T) and between strain WCC 4521(T) and S. composti LMG 23401(T) revealed DNA relatedness values of 2% (repetition, 3%) and 8% (repetition, 17%), respectively. On the basis of phenotypic and genetic properties, as well as phylogenetic distinctiveness, it is suggested that the four strains represent two novel Sphingobacterium species with strain WCC 4512(T) (=DSM 22361(T)=LMG 25272(T)) as the type strain of Sphingobacterium lactis sp. nov. (WS 4555 is a reference strain of S. lactis) and strain WCC 4521(T) (=DSM 22362(T)=LMG 25273(T)) as the type strain of Sphingobacterium alimentarium sp. nov. (WS 4556 is a reference strain of S. alimentarium).