So many simple organisms thrive in conditions that are deadly to conventional life forms that biologists believe life must have evolved under conditions dramatically different from those conditions we live with today. The first single-celled creatures on Earth could have formed during a primordial time of fire and ice about 750 million years ago when the whole planet looked something like Lake Vostok, say some biologists. There, protected from space by the ice and invigorated by the energy of the hot vents, microbes adapted and evolved in an intricate dance with extremes of heat and cold. Some microbial species find temperatures less than 194 degrees Fahrenheit to be too cold to reproduce. At the other end of the spectrum are bacteria living in the sea ice near Antarctica where it is too hot to breed if the temperature rises above 53 degrees.
Some microbes find refuge from the cold between the grains of porous stone.
Other microbes live and die in the minute gaps between snow crystals at the South Pole, biologist Ed Carpenter at San Francisco State University and USC environmental biologist Douglas Capone discovered. Those one-celled organisms were comfortable living in prolonged darkness and at temperatures so low that liquid water, which is usually a prerequisite for life on Earth, is almost completely absent. The ambient temperature in the snow where they were found hovered just above 1 degree Fahrenheit. Their habitat was continually bathed in high levels of sterilizing ultraviolet radiation common in the polar region. In order to survive in such conditions, these seemingly simple creatures each inherit four copies of their genome and an elaborate DNA repair mechanism that compensates for the destructive genetic effects of radiation and desiccation.