The bacterial SOS response sets in motion a sequence of events that activates the transfer of multiple genes for antibiotic resistance. In effect, the threatened or damaged cell becomes infectious for other bacteria and then can promote the spread of the set of genes that makes the bacteria resistant to antibiotics. This mechanism helps explain how the ability to resist multiple antibiotics can rapidly spread among bacteria. The scary thing is that, like people, bacteria are sometimes a little promiscuous: They can pass antibiotic resistance across species lines to entirely different kinds of bacteria.