world that bacteria live in. They can exchange DNA as easily as we might exchange phone numbers, money, or ideas. Sometimes, they sidle up to one another, create a physical link, and shuttle bits of DNA across: their equivalent of sex. They can also scrounge up discarded bits of DNA in their environment, left by their dead and decaying neighbours. They can even rely on viruses to move genes from one cell to another. DNA flows so freely between them that the genome of a typical bacterium is marbled with genes that arrived from its peers.
