Octadecabacter arcticus gen nov, sp nov, and O-antarcticus, sp nov, nonpigmented, psychrophilic gas vacuolate bacteria from polar sea ice and water

Heterotrophic. psychrophilic, gas vasuolate bacteria were recovered from arctic and antarctic sea ice and water. Cellular fatty acid analysis was used to group these isolates. One group herein descrihed as the new genus Octadecabacter, had octadecenoic acid (18:1) in excess of 70% of their total fatty acid content. Phylogenetic analysis of the 16S rRNA of several strains from this group revealed that they were members of the alpha Proteobacteria and were most closely related to the genus Roseobacter. Further phenotypic and genotypic tests showed that these strains can be distinguished from Roseobacter on thr basis of low levels of DNA/DNA hybridization. lack of bacteriochlorophyll a, and because they are psychrophiles. Octadecabacter gen. nov., contains both a north polar species, O, arcticus sp, nov, str, 238, and a south polar species. O. antarcticus sp. nov. str. 307. This genus may be useful for examining the extent of procaryotic biogeographic dispersal.