Temperature dependence of metabolic rates for microbial growth, maintenance, and survival.
Our work was motivated by discoveries of prokaryotic communities that survive with little nutrient in ice and permafrost, with implications for past or present microbial life in Martian permafrost and Europan ice. We compared the temperature dependence of metabolic rates of microbial communities in permafrost, ice, snow, clouds, oceans, lakes, marine and freshwater sediments, and subsurface aquifer sediments. Metabolic rates per cell fall into three groupings: (i) a rate, microg(T), for growth, measured in the laboratory at in situ temperatures with minimal disturbance of the medium; (ii) a rate, microm(T), sufficient for maintenance of functions but for a nutrient level too low for growth; and (iii) a rate, micros(T), for survival of communities imprisoned in deep glacial ice, subsurface sediment, or ocean sediment, in which they can repair macromolecular damage but are probably largely dormant. The three groups have metabolic rates consistent with a single activation energy of approximately 110 kJ and that scale as microg(T):microm(T):micros(T) approximately 10(6):10(3):1. There is no evidence of a minimum temperature for metabolism. The rate at -40 degrees C in ice corresponds to approximately 10 turnovers of cellular carbon per billion years. Microbes in ice and permafrost have metabolic rates similar to those in water, soil, and sediment at the same temperature. This finding supports the view that, far below the freezing point, liquid water inside ice and permafrost is available for metabolism. The rate micros(T) for repairing molecular damage by means of DNA-repair enzymes and protein-repair enzymes such as methyltransferase is found to be comparable to the rate of spontaneous molecular damage.
Pubmed ID: 15070769
Proceedings of the National Academy of Sciences of the United States of America
March 30, 2004
- Cell Survival
- Concentration of microbial samples in accretion ice at a depth of 3,590 m in an ice core in microbes microbial cells/ml, see BioNumbers database.
- Storage period at -20°C after which lichens recovered in lichen was 10 years, see BioNumbers database.
- Depth of Antarctic ice core from which viable microbes were extracted in microbes meters, see BioNumbers database.
- Concentration of microbial samples in accretion ice at a depth of 3,603 m in an ice core in microbes microbial cells/ml, see BioNumbers database.
- Difference between metabolic levels of growing, maintenance without growth & starving, nongrowing microbes (each) in microbes was 3 orders of magnitude, see BioNumbers database.
- Estimated average turnover rates for photosynthetic carbon incorporation in Antarctic cryptoendolithic microbial communities in microbes 1/hour, see BioNumbers database.
- Number of distinct taxa of eukaryotes identified from the Hans Tausen ice core, northern Greenland in eukaryotes was 57 taxa, see BioNumbers database.
- Fraction of total fixed ammonia that can be converted to N2O at low but finite O2 concentration in bacteria nitrosomonas spp. %, see BioNumbers database.
- Microbial concentrations are lower in clayey sediments than in sandy sediments by a factor of in microbes , see BioNumbers database.
- "Effective" activation energy for exponential growth of a community of permafrost bacteria (fed in the laboratory) in microbes kj/mole, see BioNumbers database.
- Temp. at which microbes were actively respiring in brine channels in Arctic sea ice in prokaryote °c, see BioNumbers database.
- Concentration of microbes identified from the Hans Tausen ice core, northern Greenland in microbes microbes/ml, see BioNumbers database.