In “Buried microbes exist at limit between life and death” (New Scientist, 17 May 2012), Colin Barras reports,
In a bid to hone in on the lower energy limits for life, Hans Røy at Aarhus University in Denmark probed the clays below the North Pacific gyre. Under the microscope, he found a community made up of bacteria and single-celled organisms called archaea in vanishingly small numbers.
“There are only 1000 tiny cells in 1 cubic centimetre of sediment, so finding just one is literally like hunting for a needle in a haystack.”
The microbes rely on oxygen, carbon and other nutrients in their deep environment to live, but Røy’s team found that carbon is so limited that the cells respire oxygen 10,000 times slower than bacteria in lab-grown cultures.
Røy thinks the microbial community is so sparse, and the metabolic rates so low, that the nutrient levels probably represent the bare minimum required to keep cellular enzymes and DNA working.
Well, if there is one thing we have learned since the Archaea were first discovered a couple of decades ago, it is that we oughtn’t to bet against life finding a foothold somewhere in almost any environment on Earth.
Which raises an interesting question: Why all this life is somehow here under improbable circumstances, and we never really get a signal from anywhere else? Just excuses and theories from the people who are searching. No problem with that, as long as the fact stays on the table.
Because of their remarkably slow metabolic rates, individual cells may have extremely long life spans, says Røy. The cells Morono’s team examined looked intact, yet it would take each of them hundreds or thousands of years to generate enough energy to go through cell division and produce daughter cells. That means some of Morono’s cells could be thousands of years old.
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