While suffocating, crushing, scalding, toxic and downright abysmal by most living standards, the arrangement is not so bad for Strain 121 and its ilk. They are archaea, single-celled microbes similar to, but not quite, bacteria. They often live amid extreme heat, cold, pressure, salinity, alkalinity, and/or acidity.
Archaea literally means "ancient," and Lovley and other biologists tend to call them "deep branchers" because these microbes were among the first branches on the "tree of life."
According to Lovley, Strain 121--it will be given a species name after his lab finalizes the microbe's description--uses iron the way aerobic animals use oxygen.
"It's a novel form of respiration," Lovley says, explaining how Strain 121 uses iron to accept electrons. (Many archaea also use sulfur). As oxygen does in humans, the iron allows the microbe to burn its food for energy. Chemically, the respiration process reduces ferric iron to ferrous iron and forms the mineral magnetite.
The presence of vast deposits of magnetite deep in the ocean, its presence as a respiratory byproduct of some archaea, and the abundance of iron on Earth before life began all led Lovley and Kashefi to write that "electron transport to ferrous iron may have been the first form of microbial respiration as life evolved on a hot, early Earth."
The researchers tested the process with Strain 121 cultures kept at 100 C in oxygen-free test tubes.
"It really isn't technically difficult. You just need some ovens to get it hot enough--and remember not to pick it up with your bare hands," Lovley says, speaking from experience.
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Contact: Sean Kearns
skearns@nsf.gov
703-292-7963
National Science Foundation
14-Aug-2003