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

Abstract

Lactose killing is a peculiar phenomenon in which 80-98% of the E. 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 causes 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, were eliminated. Rapid uptake of sugars by the lactose permease apparently disrupts membrane function, perhaps causing collapse of the membrane potential.