Phylogenetic study of the genus Oceanospirillum based on 16S rRNA and gyrB genes: emended description of the genus Oceanospirillum, description of Pseudospirillum gen. nov., Oceanobacter gen. nov. and Terasakiella gen. nov. and transfer of Oceanospirillum jannaschii and Pseudomonas stanieri to Marinobacterium as Marinobacterium jannaschii comb. nov. and Marinobacterium stanieri comb. no.

The phylogenetic relationships of Oceanospirillum strains were analysed by using the nucleotide sequences of 16S rRNA and gyrB genes. Results from sequence analysis demonstrated that the Oceanospirillum core group consisted of four species, Oceanospirillum linum, Oceanospirillum maris, Oceanospirillum beijerinckii and Oceanospirillum multiglobuliferum, with enough distance to separate them as different species. However, four other Oceanospirillum species occupied taxonomic positions separate from the Oceanospirillum core group: Oceanospirillum jannaschii, Oceanospirillum japonicum and Oceanospirillum kriegii in the gamma-Proteobacteria and Oceanospirillum pusillum in the alpha-Proteobacteria. Oceanospirillum jannaschii clustered with Marinobacterium georgiense, Pseudomonas iners and Pseudomonas stanieri on the basis of phylogenetic analysis of 16S rRNA and gyrB genes. The other three species did not cluster with known genera. Also, the sequence similarity values of the gyrB genes between the three subspecies of Oceanospirillum maris and those between the two subspecies of Oceanospirillum beijerinckii were above 99%. The close relationships between the subspecies of Oceanospirillum maris and of Oceanospirillum beijerinckii were further supported by similar physiological properties and high DNA-DNA hybridization values, suggesting that these subspecies should not be regarded as valid. From these results, Oceanospirillum sensu stricto should be defined to consist of Oceanospirillum linum, Oceanospirillum maris, Oceanospirillum beijerinckii and Oceanospirillum multiglobuliferum. We propose to create the following new genera: Pseudospirillum gen. nov. for Oceanospirillum japonicum as Pseudospirillum japonicum comb. nov.; Oceanobacter gen. nov. for Oceanospirillum kriegii as Oceanobacter kriegii comb. nov.; and Terasakiella gen. nov. for Oceanospirillum pusillum as Terasakiella pusilla comb. nov. The transfer is proposed of Oceanospirillum jannaschii and Pseudomonas stanieri to Marinobacterium as Marinobacterium jannaschii comb. nov. and Marinobacterium stanieri comb. nov. Furthermore, Pseudomonas iners should be reclassified as a strain of Marinobacterium georgiense. Finally, the subspecies of Oceanospirillum maris (O. maris subsp. maris, O. maris subsp. hiroshimense and O. maris subsp. williamsae) and Oceanospirillum beijerinckii (O. beijerinckii subsp. beijerinckii and O. beijerinckii subsp. pelagicum) should be combined as Oceanospirillum maris and Oceanospirillum beijerinckii, respectively.