Taxonomy and Biogeography of Polar Sea Ice Bacteria

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During the winter the temperature becomes sufficiently low for sea water to freeze in high latitude polar regions. The layer of ice on the sea may thicken to over two yards in depth. As the following spring approaches, microorganisms begin growing in the lower foot of the sea ice. This community of sea ice microorganisms is dominated by sea ice algae that grow to sufficient density to impart a red to brown color to the lower layer. Bacteria derive nutrients from the ice algae and grow with them in the layer. Although considerable work has been performed on the sea ice algae, little is yet known about the kinds of bacteria that grow in this cold environment. Dr. James Staley of the University of Washington has collected sea ice bacteria from both antarctic and arctic zones and has discovered novel forms, some with specialized gas vacuoles in their cells. Using standard bacteriological tests as well as newer molecular methods of DNA analysis, including ribosomal gene sequencing, Dr. Staley is characterizing the various bacterial strains collected from polar sea ice. One objective is to determine whether the same species of bacteria occur in both the north and south polar ice communities. Another objective is to assay the range of taxonomic diversity present in the two geographically separate regions. Knowledge about true cold-adapted bacteria would have eventual implications for decomposition and waste disposal in polar regions and cold marine waters.