Transport by the lactose permease of Escherichia coli as the basis of lactose killing.

Lactose killing is a peculiar phenomenon in which 80 to 98% of the Escherichia coli cells taken from a lactose-limited chemostat die when plated on standard lactose minimal media. This unique form of suicide is caused by the action of the lactose permease. Since uptake of either lactose or galactose by the lactose permease caused death, the action of rapid transport across the membrane must be the cause of the phenomenon. Alternative causes of lactose killing, such as accumulation of toxic metabolic intermediates or action of the beta-galactosidase, have been eliminated. It is proposed that rapid uptake of sugars by the lactose permease disrupts membrane function, perhaps causing collapse of the membrane potential.