Researchers have found a new form of energy metabolism in extremely heat-loving (hyperthermophilic) microbes from the genus Thermococcus, which thrive at temperatures above 80 deg C.
Yun Jae Kim, Hyun Sook Lee, and colleagues from several research institutes in Korea, Japan and Russia, demonstrated that several Thermococcus species can produce the cellular energy currency, ATP, using formic acid, the simplest organic acid, as their only fuel. They react formic acid with water, producing bicarbonate and molecular hydrogen.
The researchers discovered the surprising ability in the species T. onnurineus after noticing that its genome contained multiple copies of a gene coding for an enzyme specific for the oxidation of formic acid. When they tested other Thermococcus species for this trait, several, but not all shared the ability to thrive on formic acid. Thermococci form part of the domain of the Archaea, which are as distinct from the Bacteria as from the Eukarya (including all plant and animal species), and which include many species adapted to life under extreme conditions.
Previously, biologists had assumed that this type of reaction would not yield enough energy to fuel the growth of cells. Formate consumption was only known from microbial communities where methane producers can use the hydrogen produced and thereby favour the reaction.
This represents the simplest anaerobic (i.e. oxygen-excluding) metabolism discovered so far, and may well point to ancestral, primitive forms of energy metabolism that were later superseded by more efficient types in most branches of life.
Kim et al, Nature 2010, 467, 352.
For background information on extremophiles, see my book:
Life on the Edge