Effect of carbon dioxide and aging on the dihydrostreptomycin inhibition of pyruvate fermentation in Escherichia coli.

Barkulis (1953) demonstrated that resting cells of a strain of Escherichia coli ferment pyruvate in bicarbonate buffer chiefly by way of the phosphoroclastic reaction and that pyruvate fermentation is strongly inhibited by low concentrations of dihydrostreptomycin. When this work was almost completed, Umbreit and Oginsky (1951) found that anaerobic pyruvate breakdown in their strains of E. coli is inhibited by streptomycin only in the presence of carbon dioxide and bicarbonate. These experiments were carried out to determine the effect of carbon dioxide on the dihydrostreptomycin inhibition of pyruvate ferinentation in the strain E. coli studied by Barkulis (1953). Dihydrostreptomycin had almost no effect on pyruvate fermentation in freshly prepared resting cellular suspensions when carbon dioxide was excluded from the test system. This finding confirms the observation of Umbreit and Oginsky (1951) with respect to fresh cellular suspensions. However, when the celLs were aged at 2 C, the dihydrostreptomycin inhibition in the absence of carbon dioxide rapidly increased, and within one to two weeks dihydrostreptomycin almost completely prevented all anaerobic pyruvate removal, both in the presence and in the absence of carbon dioxide. These data suggest the existence of at least two main pathways of pyruvate fermentation in fresh cellular suspensions of E. coli with different carbon dioxide requirements and different susceptibilities to dihydrostreptomycin.