Killing and Lysis of Escherichia coli in the Presence of Chloramphenicol: Relation to Cellular Magnesium

Treatment ofEscherichia coli K-10 with 100 μg of chloramphenicol per ml for periods greater than 30 min leads to progressive lysis and killing of cells. The bactericidal action of the antibiotic is dependent on cell growth and physiology; only rapidly dividing cells are susceptible to killing; resting or slowly growing cells are not. The presence of excess Mg2+ in the growth medium specifically and competitively prevents excretion of macromolecules and cell lysis. However, inhibition of protein synthesis and killing of cells still occur even in the presence of added Mg2+ . The possible relation of these effects to the mode of action of chloramphenicol is discussed.