Cohen et. al report, in Nature Microbiology, that the addition of ampicillin, cephalexin or pipericillin will cause E. coli to induce the SOS response. The SOS response is an emergency repair system microbes will turn on when the surrounding environment turns ugly. There are a number of signals that will turn on the SOS response, but the classic inducer is DNA damage. It is now clear that antibiotics will also turn on this response and prevent the cell from dividing and growing. This in turn will make them better able to withstand the harmful effects of the drug they are facing. With this knowledge it may be possible to create effective drugs that inhibit the SOS response, making E. coli and other microbes more susceptible to antibiotics.