Researchers have found bacteria that live in rocks 2.8 kilometers below Earth's surface and rely on radioactive uranium to convert water molecules to useable energy.

Using "grammar" as their guide, scientists could easily produce tens of thousands of new bacteria-fighters and test them for use as future drugs

Bacteria are so important to key functions such as digestion and the immune system that we may be truly symbiotic organisms -- relying on one another for life itself, the scientists write in Friday's issue of the journal Science.