Normal 0 false false false MicrosoftInternetExplorer4 A fracture deep underground in a South African gold mine holds a rare biological find — an ecological system populated by a single species of bacteria. An analysis of the bacterium’s complete genetic makeup, published October 10 in Science, reveals that the bacteria have all the tools to survive completely alone.
“This really stands one of the basic tenets of microbial ecology on its head,” says Carl Pilcher, director of the NASA Astrobiology Institute at the NASAAmesResearchCenter headquartered at Mountain View, Calif. Based on experience with other ecosystems, scientists thought that any microbial community would contain a variety of species, each specialized to grow on different nutrients. Some microbes would use nutrients found in the environment and make byproducts that other microbes could use to grow.
Not only does the newly characterized bacterium live alone, but it also appears to live independently of the sun-powered system that helps nourish all other organisms on, or in, the Earth. (Even bacteria that get their energy from chemical reactions get some nutrients indirectly from solar energy.) “This is the first pretty solid evidence that there is another source of energy life can use, and that is radioactive energy,” says Pilcher, who was not part of the team that discovered and analyzed the bacterium. The finding indicates that other rocky planets could support subsurface life that grows on a similar energy source, he says.
In recent years, DNA studies of oceans and other places where microorganisms live have revealed intensely diverse microbial communities. That trend is reversed the lower you go into the Earth’s crust. At about three kilometers deep, the Mponeng gold mine in South Africa is about as low as anyone has gone into the solid Earth.