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Project Progress

We continue to study life in saline ice formations, taking a multi-facetd approach that includes work on Bacteria, Archaea, viruses, exopolymers (EPS) and extracellular enzymes. Attachment or sorption to surfaces (first-stage biofilm formation) under extreme conditions provides an important focal point. Accomplishments this year stem from work with our model cold-adapted bacterium, Colwellia psychrerythraea strain 34H, and with field samples collected last year. A comparative whole-genomic and proteomic analysis of our Colwellia strain was completed and published (Methé et al., 2005); highlights include clear distinction of the psychrophilic proteome from proteomes of other thermal classes, an apparent record number of encoded proteins and other compounds destined for export from the cytoplasm, and potential evidence of lateral gene transfer (presence of Archaeal genes and two apparently complete viral genomes). Former post-doc Junge obtained evidence for EPS-enhanced leucine incorporation into protein by Colwellia cells down to —20°C (and for activity at sub-eutectic temperatures, originally expected to yield negative controls). New post-doc Marx verified Colwellia over-production of EPS under conditions of temperature, pressure , and salinity stress, with design of planned sub-eutectic experiments improved by co-I Eicken. These studies reinforce the importance of EPS to microbial survival in extreme habitats and possibly as biosignatures on icy planets and moons. From fieldwork in the Arctic (winter 2004), the PI obtained evidence for protease activity in saline ice at new temperature lows (down to —18°C; Deming, 2004), while graduate student Collins amplified Archaeal genes from winter ice (not known from warmer ice) and doctoral candidate Wells demonstrated viral lysis of bacteria, as well as bacterial growth, in ice brines at —12°C (Wells and Deming, submitted). Wells also completed work on the source and distribution of Archaea in subzero Arctic waters during autumn (Wells et al., submitted) and on characterization of a novel cold-active virus (the most heat-labile known) from this environment that lyses our Colwellia strain. The presence of Archaea in autumn waters and winter sea ice, detection of a dynamic microbial-viral community in winter ice, and availability of a model viral-bacterial host system (where the host contains Archaeal genes and other viruses) lead to hypothesis development regarding microbial evolution and gene exchange in saline ice formations, environments threatened with extinction on Earth (especially in the Arctic) due to climate warming and recently reported on Mars.