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 fr om arctic and antarctic sea ice and water. Cellular fatty acid analysi s 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 member s of the alpha Proteobacteria and were most closely related to the gen us Roseobacter. Further phenotypic and genotypic tests showed that the se strains can be distinguished from Roseobacter on thr basis of low l evels of DNA/DNA hybridization. lack of bacteriochlorophyll a, and bec ause 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 f or examining the extent of procaryotic biogeographic dispersal.