Tuesday, 7 October 2008: 8:25 AM
George R. Brown Convention Center, 310BE
The springs at Gypsum Hill (GH) and Colour Peak (CP) on Axel Heiberg Island in the Canadian high Arctic are among the few known examples of perennial cold springs emanating through thick permafrost on Earth. The springs discharge cold anoxic brines that contain high concentrations of both sulfate and sulfide. DNA-based analyses of the microbial communities inhabiting the spring sediments indicated that sequences related to the S-oxidizing bacterium Thiomicrospira dominated both the GH and CP bacterial libraries with 56 to 76% of the sequences being from potential S-metabolizing bacteria. During the winter months conspicuous grey-colored filamentous biomass also form in snow-covered run-off channels originating from the GH springs. Culture and molecular-based analyses proved that the filamentous community is completely dominated by Thiomicrospira. The filaments also undertake sulfide and thiosulfate oxidation and CO2 fixation under in situ spring conditions, which is consistent with the presence and activity of chemolithoautotrophic S-oxidizing bacteria such as Thiomicrospira. These results suggest that the cycling and utilization of S compounds may play a major role in the energy production and maintenance of microbial communities in these unique, cold environments.