期刊
CANADIAN JOURNAL OF MICROBIOLOGY
卷 55, 期 1, 页码 1-11出版社
CANADIAN SCIENCE PUBLISHING
DOI: 10.1139/W08-117
关键词
cold origin of life; microbial habitats in ice; metabolic rate; bacteria and phages; starvation and death
资金
- Office of Polar Programs (OPP) [0738658] Funding Source: National Science Foundation
Arguments are given that terrestrial RNA and DNA may have originated in a frozen environment more than 4 billion years ago. Scenarios are developed for atmospheric transport of microbes onto glacial ice, their adaptation to subzero temperatures in the ice, and their incorporation into one of three habitats - liquid veins, mineral grain surfaces, or isolated inside 1 of the crystals that make up polycrystalline ice. The Arrhenius dependence of microbial metabolic rate on temperature is shown to match that required to repair damage owing to spontaneous DNA depurination and amino acid racemization. Even for the oldest glacial ice, microbial lifetime is shown not to be shortened by radiation damage from U-238, Th-232, or K-40 in mineral dust in ice, by phage-induced lysis, or by penetrating cosmic radiation. Instead, death of those cells adapted to the hostile conditions in glacial ice is probably due to exhaustion of available nutrients. By contrast, in permafrost microbial death is more likely due to alpha-particle radiation damage from U and Th in the soil and rocks intermixed with ice. For residence times in ice longer than a million years, spore formers may be unable to compete in longevity with vegetative cells that are able to repair DNA damage via survival metabolism.
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