Vibrio casei sp nov., isolated from the surfaces of two French red smear soft cheeses

Three Gram-negative, rod-shaped, catalase- and oxidase-positive, facultatively anaerobic and motile bacteria, strains WS 4538, WS 4539(T) and WS 4540, were isolated from the surfaces of two fully ripened French red smear soft cheeses. Based on 16S rRNA gene sequence similarity, all three strains were shown to belong to the genus Vibrio. They are most closely related to Vibrio rumoiensis S-1(T) (96.3% similarity) and Vibrio litoralis MANO22D(T) (95.9%). DNA-DNA hybridization confirmed that all three isolates belong to the same species and clearly separated strain WS 4539T from V. rumoiensis DSM 19141(T) (38-42% relatedness) and V. litoralis DSM 17657(T) (28-37%). In contrast to their nearest relatives, the strains exhibited beta-galactosidase and aesculin hydrolase activities. A 14 bp insertion in the 16S rRNA gene sequence forms an elongated structure at helix 10 in the rRNA molecule and provides a tool for PCR-based identification of the novel species. Partial sequences of the housekeeping genes atpA, recA, rpoA and pyrH supported the conclusion that the three isolates constitute a separate species within the genus Vibrio. The name Vibrio casei sp. nov. is proposed for the novel taxon. Strain WS 4539T (=DSM 22364(T) =LMG 25240(T); DNA G+C content 41.8 mol%) is the type strain and WS 4540 (=DSM 22378 =LMG 25241) is a reference strain.