Scientists have discovered a population of bacteria thriving 2.8 kilometres underground, which rely on radiation produced by uranium for survival. The findings make the existence of life elsewhere in the universe much more likely. The discovery, which is published in his week's Science, was made in a South African gold mine near Johannesburg. Hearing about a new water-filled fracture uncovered in the mine, Indiana University Bloomington researcher Lisa Pratt and her colleagues collected samples of the water emanating from the fracture. They used various chemical isotope techniques to date how long the water had been isolated underground, and DNA methods to identify the populations of bacteria it contained. The analysis showed that the water had been trapped underground for between 15 and 25 million years old, meaning that the bacteria it contained must date from at least that time. The DNA tests revealed a host of bacteria but one poulation dominated - a new species closely related to bacteria found at hydrothermal vents referred to as Furmicutes. These organisms are adapted to consume hydrogen and sulphur compounds which are released when minerals are zapped by radiation from decaying uranium, which is also present in the rock. The bi-products and metabolites of the Furmicutes then sustain the other species of bacteria. Previously, scientists had always thought that all forms of life on earth depended, albeit indirectly, on energy from the sun. But these bacteria, which have essentially existed on the energy provided by low-level natural radioactivity for millions of years, prove that's not the case. And at the same time they greatly increase the odds of life evolving to exist in similar conditions elsewhere in the universe...


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