HR: 16:45h
AN: C12C-04    [PDF]
TI: Microbial Metabolism in Permafrost and Ice
AU: * Price, P B
EM: bprice@uclink.berkeley.edu
AF: University of California, Physics Department, Berkeley, CA 94720 United States
AU: Bramall, N
EM: bramall@socrates.berkeley.edu
AF: University of California, Physics Department, Berkeley, CA 94720 United States
AU: Bay, R C
EM: bay@cletus.physics.berkeley.edu
AF: University of California, Physics Department, Berkeley, CA 94720 United States
AB: Metabolic rates of microbial communities at low temperature have not been systematically studied, despite discoveries of microbes that survive with very little nutrient in ice, permafrost, and deep open-ocean sites, and despite interest in possible life on Mars and Europa. We investigated the temperature-dependence of growth rates kg, maintenance rates km, and survival rates ks, using existing data on kg(T) for permafrost bacteria, on km(T) using radiotracers, and on ks(T) using geochemical methods. Data were collected for temperatures from 28$\deg$C to -40$\deg$C. The rates for the three modes are consistent with a single activation energy U $\approx$ 100-110 kJ/mol, and they scale as kg(T):km(T):ks(T) $\approx$ 107:104:1. The rate ks(T) for survival of a dormant microbial community is found to be roughly that required solely for repairing molecular damage due to amino acid racemization + DNA depurination. We conclude that for living microbes the rate of molecular repair equals the rate of molecular damage. There is no indication of a threshold temperature for metabolism, at least down to -40$\deg$C. To assay microbial life in the coldest terrestrial environments (down to -55$\deg$C) and in future to search for present or past life on Mars, we have designed a miniaturized biospectral logger that will fit into a 4-cm borehole in ice, permafrost and rock. The logger will use side-directed laser beams at wavelengths 224 and 370 nm to detect autofluorescence of biomolecules and discriminate against mineral autofluorescence. Six channels will map fluorescence spectra and a seventh channel will measure light scattered from dust (in ice) or rock (in permafrost). Fluorescent biomolecules of interest include tryptophan, tyrosine, NADH, FAD, F420, chlorophyll, bacteriorhodopsin, porphyrins, pyoverdin, PAHs, humic acid, and fulvic acid. The logger will be able to detect microbial concentrations as low as 1 cell cm-3 in clean ice.
DE: 0400 Biogeosciences
DE: 0915 Downhole methods
DE: 1823 Frozen ground
DE: 5462 Polar regions
DE: 5494 Instruments and techniques
SC: Cryosphere [C]
MN: 2003 Fall Meeting