[Role of metabolic energy in the regulation of chlortetracycline transport in Escherichia coli].

The uptake of chlorotetracycline by the E. coli K-12 strain sensitive to this antibiotic and by its resistant mutant E. coli E-6-X is regulated by the antibiotic transport being coupled and uncoupled with the metabolic energy, this being determined by the concentration of chlorotetracycline in the medium. If the level of the antibiotic is lower than the subbacteriostatic concentration, its accumulation by both strains requires the metabolic energy and can be suppressed by formaldehyde or 2,4-dinitrophenol. As the concentration of chlorotetracycline increases, it is no more absorbed by the cells of the sensitive strain, via the active transport and its accumulation does not change in the presence of 2,4-dinitrophenol or glucose. In the resistant strain, the mechanism of the energy-dependent transport of chlorotetracycline from the cells starts to function: the accumulation of the antibiotic decreases in the presence of glucose and increases in the presence of 2,4-dinitrophenol.