Earth teems with bacteria-eating viruses. There are perhaps 10 times as many of these viruses as of all other living things put together. Yet researchers don't know how many virus species there are, how they are distributed around the globe, or how diverse their genes are. Now, a team of scientists has begun to answer those questions, completing the first survey of virus DNA in oceans around the world.
Scientists knew that each milliliter of ocean water holds about 50 million virus particles and that those organisms kill 20 percent of the bacteria in the ocean every day (SN: 7/12/2003, p. 26: All the World's a Phage). In the process, viruses move gene sequences from one bacterium to another, speeding evolution and turning some bacteria virulent.