Applied and Environmental Microbiology, August 2000, p. 3214-3220, Vol. 66, No. 8
0099-2240/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta, Canada, T6G 2E3,1 and Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada, T6G 2E92
Received 27 January 2000/Accepted 26 May 2000
The debris-rich basal ice layers of a high Arctic glacier were
shown to contain metabolically diverse microbes that could be cultured
oligotrophically at low temperatures (0.3 to 4°C). These organisms
included aerobic chemoheterotrophs and anaerobic nitrate reducers,
sulfate reducers, and methanogens. Colonies purified from subglacial
samples at 4°C appeared to be predominantly psychrophilic. Aerobic
chemoheterotrophs were metabolically active in unfrozen basal sediments
when they were cultured at 0.3°C in the dark (to simulate
nearly in situ conditions), producing 14CO2
from radiolabeled sodium acetate with minimal organic amendment (
38
µM C). In contrast, no activity was observed when samples were
cultured at subfreezing temperatures (
1.8°C) for 66 days. Electron microscopy of thawed basal ice samples revealed various cell
morphologies, including dividing cells. This suggests that the
subglacial environment beneath a polythermal glacier provides a viable
habitat for life and that microbes may be widespread where the basal
ice is temperate and water is present at the base of the glacier and
where organic carbon from glacially overridden soils is
present. Our observations raise the possibility that in situ microbial production of CO2 and CH4
beneath ice masses (e.g., the Northern Hemisphere ice sheets) is an
important factor in carbon cycling during glacial periods. Moreover,
this terrestrial environment may provide a model for viable habitats
for life on Mars, since similar conditions may exist or may have
existed in the basal sediments beneath the Martian north polar ice cap.
This is Polar Continental Shelf Project contribution 00199.
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