Robertson Glacier, Alberta, Canada is situated in a northern facing catchment in the Canadian Rockies. The catchment bedrock is carbonate with interbeds of shale, both of which contain trace amounts (~ 1%) of pyrite. Physical comminution of the bedrock by the glacier provides fresh mineral surfaces capable of sustaining light independent microbial communities. Indeed, our work has shown that pyrite is the primary source of reductant supporting aerobic microbial communities that associate with subglacial sediments and physical shearing of silicate minerals, followed by reactions of silica radicals with water, supplies abundant hydrogen capable of sustaining an abundance of anaerobic, hydrogenotrophic methanogens. To this end, Robertson Glacier serves as a useful model for investigating the interaction of physical processes (bedrock comminution) and water rock interactions in sustaining microbial life in cold, subglacial habitats. These habitats are analogs for potential subglacial habitats on Mars and other planetary bodies.Â
Research conducted by RPL in 2016 focused on examining the role of a cultivar isolated from Robertson Glacier sediments in the oxidation of thiosulfate, a pyrite oxidation intermediate. Thiobacillus strain RG5, when cultivated at 5°C, catalyzed the oxidation of thiosulfate coupled with reduction of oxygen or nitrate. Importantly, growth yields were higher and generation times lower at 5°C when compared to 15°C, indicating that the strain is cold adapted. Molecular analyses confirm that the strain is active in situ. Additional work being conducted on sediments from Robertson Glacier include an analysis of iron reducing isolates growing on a variety of solid phase iron sources. Data from these projects will expand our understanding of the physiological processes that allow for life to thrive in cold, dark environments supported by mineral forms of energy.
