The control by respiration of the uptake of alpha-methyl glucoside in Escherichia coli K12.

The uptake of methyl alpha-D-glucopyranoside (alpha-MG) by Escherichia coli K12 was decreased by the addition of substrates which stimulated the rate of oxygen consumption by the cells. The inhibition, which occurred only at non-saturating concentrations of alpha-MG, was not the result of a stimulation of the rate of exit of intracellular alpha-MG, and was abolished by the presence of carbonyl cyanide m-chlorophenylhydrazone or sodium azide. Since those drugs inhibit energy conservation at the respiratory chain and did not alter significantly the rate of oxygen consumption under the conditions for the assay of alpha-MG uptake, it appears that the inhibition of the transport system by respirable substrates is mediated by some form of energy derived from respiration.