The inhibitory effect of salt, cyanide and chloramphenicol on the uptake of streptomycin by Escherichia coli K 12.

The uptake of tritium-labelled streptomycin by cells of Eschericia coli K 12 was shown to be only partly and transiently inhibited by the reported antagonists cyanide and chloramphenicol. After a lag, uptake of streptomycin took place in the presence of cyanide, although at a decreased rate. The lag was absent when cells were treated with cyanide some time before streptomycin. The cyanide-resistant transport system showed the same sensitivity to salt as the normal system. By increasing the salt content of the complex medium used, the uptake rate was decreased and several different phases in the uptake became detectable, including an early saturation phase of unknown nature. Uptake in a mineral salt medium was compared with that in complex medium, and differences in uptake were found explainable by differences in salt content. Chloramphenicol, in a concentration of 50 microgram/ml, was shown to permit an uptake rate (after a lag) of about one-fifth of the normal uptake rate in the complex medium. When the last rapid uptake phase, coincident with killing, was delayed by salt or cyanide, chloramphenicol had little or no effect on uptake. At higher concentrations, it enhanced the uptake and caused lysis of the bacteria. Based on the inhibition pattern produced by the inhibitors mentioned above, both alone and in combination, a hypothesis for the uptake of streptomycin by Escherichia coli is submitted.