Microbial Biodiversity in Permafrost Ground Ice Samples and Survival of High Arctic isolate Cryptococcus NP33 under simulated Martian Conditions

The work in this thesis consisted of two studies: (1) analysis of the microbial biodiversity of multiple ground ice types from the Arctic and the High Arctic; (2) examination of the survival of Cryptococcus NP33 under simulated Martian conditions over 41 days. The first study involved culture-dependent and independent evaluations of the microbial communities found in a buried firnified snow bank, a buried glacier, a pingo and ice wedges. Direct and culturable counts in the various ground ice types differed from each other (104 -- 108 cells·mL -1 direct counts; 0 - 105 CFU·mL-1 culturable counts), and were only weakly correlated to increasing sample age. Culturable counts were consistently highest in ice wedge samples. All sample isolates were dominated by Actinobacteria. Bacterial pyrosequencing analysis for one ice wedge showed a dominance (<50% of sequences) by Gammaproteobacteria. In an Archaeal clone library of the buried glacier, no clones were closely related to sequenced isolates, but were similar (>90%) to uncharacterized clones from marine environments. The pingo Bacterial clone library clones matched closely to environmental isolates as well as clones from cryoenvironments as well as soil environments. For the survivability study, Cryptococcus strain NP33 was selected as a candidate organism to undergo Martian simulations. After 41 simulation days, it had a half-life of 10.1 days in simulated sunlight and 16.1 days in darkness. The compiled results suggest that the organism traits most crucial to survival under simulated Martian conditions were desiccation, radiation and freeze-thaw resistance.