Induction of the SOS response in starved Escherichia coli.

The SOS system in Escherichia coli is induced in response to DNA damage and the arrest of DNA synthesis. Here we show that in AB1157 bacteria starved for arginine, conditions for induction of adaptive mutations, the LexA-dependent SOS system is induced, but that this occurs only when the bacteria resume growth and when the source of carbon is glycerol rather than glucose (glycerol, but not glucose, enables synthesis of cAMP). Therefore, we conclude that starved cells accumulate some lesions in DNA, which in growth conditions may trigger SOS induction by a process that is cAMP-dependent.