Microorganisms that live below the surface of the earth remain one of the last great areas of exploration. Organisms that live there have not been cultured in the laboratory and therefore their lifestyles are unknown.
An international team from the University of Texas, Uppsala University, UNC Chapel Hill, and the University of Bremen, have discovered how microorganisms, first discovered in a South African gold mine at a depth of about 3 km, are able to make a living in the absence of oxygen and light.
In order to understand these elusive organisms, the colleagues sequenced the genomes of several species. They were able to determine how these microbes should be classified and what physiological tricks they use to thrive under these extreme conditions with temperatures of up to 80°C. These organisms live in areas devoid of oxygen and the researchers suggest that they are able to survive by using carbon monoxide for energy production. The chemical pathways the cells use to metabolize carbon monoxide are unique and have not seen anywhere else before.
As this new group of microbes is specialized for survival beneath the surface, the colleagues called them Hadesarchaea, after the ancient Greek god of the underworld. As its name suggests, the Hadesarchaea belong to the archaea, a relatively unknown group of microorganisms. Archaea were discovered only some 40 years ago, by Carl Woese. They were initially classified as bacteria, but this classification is outdated. From an evolutionary perspective, both groups differ more from each other than a human does from a tree. Many species in this group have been found thriving in acidic hot springs and salt likes, environments that would be uninhabitable to most other life forms. To date, archaea remain poorly studied in comparison to bacteria and other life forms, such as animals and plants.