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Project Progress

In the first year of this award, we have begun to build conceptual models and rationales for first-stage biofilm formation by bacteria under the extreme conditions in ice, considering in particular the role of bacterial motility (Allen and Deming, 2002) and attachment (Junge et al., 2002a, 2002b, 2002c) as the eutectic point of water is approached (Deming, 2002). Since salinity influences the eutectic point as well as bacterial activity, the composition and concentration of salts in the parent water becomes a central issue (Deming and Eicken, 2002). Building upon our previous work with sea ice (supported by NSF), we adapted the in situ microscopic imaging method that we had developed for sea ice to the similar examination of freshwater ice, using natural Arctic lake ice as the test medium. We obtained the first images of bacteria packed within the fine veins of fluid between the microscale ice crystals of the lake ice (Junge et al., 2002a, 2002b). The space available for the bacteria, however, was limited compared to sea ice at a comparable temperature (at 5C). We also conducted tests for bacterial motility at subzero temperatures and documented unambiguous movement at 10C in the presence of glycerol; salt constraints are next to consider systematically.