Torahiko Okubo¹, Yuika Tosaka¹, Toyotaka Sato¹, Masaru Usui¹, Chie Nakajima², Yasuhiko Suzuki², Satoshi Imura³, Yutaka Tamura^1,

In order to reveal the diversity of sea ice bacterial communities in polar and sub-polar regions, we investigated 2 drifting ice floes, one from the Australian side of the Southern Ocean and the other from the Sea of Okhotsk. We extracted bacterial DNA from sea ice and constructed 221 16S rDNA clone libraries including 109 clones from the Antarctic sea ice and 112 from the Okhotsk sea ice. The phylogenetic analysis of 16S rDNA sequences showed that Roseobacter and Sulfitobacter (Alphaproteobacteria), Psychrobacter, Halomonas, and Pseudoalteromonas (Gammaproteobacteria) were frequent in the Antarctic sea ice; Colwellia, Psychromonas, and Glaciecola (Gammaproteobacteria) and Polaribacter (Bacteroidetes) were major genera in the Okhotsk sea ice. While Alphaproteobacteria and Gammaproteobacteria were abundant in both samples, Bacteroidetes were detected only in the Okhotsk sea ice. Comparing the bacterial diversity of our samples with that of other studies, bacterial communities in sea ice were similar to one another at the phylum level, whereas their populations were quite different at the genus level. We also tried to detect antimicrobial and heavy metal resistance genes in our samples but didn’t identified. Our results provide additional information about the bacterial communities in sea ice.

16S rDNA-based analysis, bacterial diversity, sea ice, Sea of Okhotsk, Southern Ocean