Streptomycin lethality and cyclic AMP

Abstract

The action of low and moderate concentrations of streptomycin has been studied with Escherichia coli B growing in synthetic media with glucose or glycerol as the carbon source. The inception of lethality depended on the carbon source and the presence of cyclic AMP or ATP in the growth medium. At low concentration of streptomycin (2.5 μg/ml), cells in salts-glycerol media lost their viability following two and a half hour lag period. Glucose repressed the bactericidal effect of streptomycin allowing the cells to grow normally although at a slightly reduced rate. The addition of cyclic AMP to the growth medium reversed glucose repression and rendered the cells sensitive to the action of the drug. At higher concentrations of streptomycin (up to 20 μg/ml) glucose and ATP prolonged and glycerol and cyclic AMP shortened the lag before the cells began to lose their viability. At streptomycin concentration of 5 μg/ml, ATP protected the cells against the bactericidal effect of the drug allowing them to grow normally. This effect of ATP could be abolished by the addition of cyclic AMP. At streptomycin concentrations above 20 μg/ml, the effect of glucose, cyclic AMP and ATP was no longer measurable.