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Project Progress

We continue to pursue questions on microbial activity and evolution in subzero salty habitats, taking a multi-faceted approach that includes studies of Bacteria, Archaea, viruses, exopolymers and extracellular enzymes. The phenomenon of attachment or sorption to surfaces (first-stage biofilm formation) under extreme conditions of temperature and salt concentration provides an important focal point. Although much of our work is influenced by NAI objectives, specific accomplishments this year stem from three efforts. Postdoctoral work by Karen Junge has yielded evidence that high molecular weight polymeric substances (EPS), derived from the spent medium of cold-adapted bacterium Colwellia psychrerythraea strain 34H, facilitate bacterial activity (incorporation of tritiated leucine into macromolecules) at temperatures below —20°C (Junge et al., in preparation). This work reinforces the importance of EPS to microbial survival (and continuing evolution) in deeply frozen environments, as well as the potential of EPS as biosignatures on icy planets and moons. Work by the PI (on sabbatical leave this year) during an over-wintering expedition in the Arctic included development of new approaches to studying enzyme activity in natural and unmelted ice formations. Sea-ice samples laden with particles or EPS gave the most promising results (in keeping with earlier work by Junge et al., 2004). Theoretical considerations to improve the design of experiments in deeply frozen systems were then developed jointly with co-I Eicken during sabbatical time in Fairbanks . Work by doctoral candidate Llyd Wells has resulted in numerous accomplishments this year, including a detailed phenotypic characterization of a cold-adapted phage-host system, using novel techniques developed for work at low temperature, and presumptive evidence for horizontal gene transfer in the cold using a genomic approach. Viral activity was also measured in field samples (again paying attention to particle-rich samples, as well as those that may contain Archaea) under various extreme conditions, including low temperature, limited host-food availability, and the subzero salty conditions of winter-time sea-ice brines. Although these efforts have not yet been brought to publication, other work reported last year has reached the press (see reference list).