Taxonomic studies of extremely barophilic bacteria isolated from the Mariana Trench and description of Moritella yayanosii sp. nov., a new barophilicbacterial isolate

We have isolated two strains of extremely barophilic bacteria from sediment collected from the world's deepest ocean floor in the Mariana Trench, Chal lenger Deep, at a depth of 10898m [Kato C, Li L, Nogi Y, Nakamura Y, Tamaok a J, Horikoshi K (1998) Appl Environ Microbiol 64:1510-1513]. One strain, D B21MT-2, was identified as a strain of Shewanella benthica, and the other s train, DB21MT-5, is closely affiliated with members of the genus Moritella on the basis of 168 rDNA sequence analysis. The hybridization values for DN A-DNA relatedness between DB21MT-5 and the Moritella reference strains were significantly lower than that accepted as the phylogenetic definition of a species. Based on this and other taxonomic differences, strain DB21MT-5 ap pears to represent a novel obligately barophilic deep-sea Moritella species . The name Moritella yayanosii (JCM 10263) is proposed. This is the first p roposed species of obligately barophilic bacteria of the genus Moritella.