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Abstract
Some factors which affect the killing by streptomycin of Staphylococcus aureus in growing cultures have been investigated. In short-term experiments, streptomycin is not bactericidal under conditions in which growth of the organisms cannot occur (low temperature, absence of nitrogen source, presence of growth-inhibitory concentrations of chloramphenicol). The rate of killing of organisms growing anaerobically is considerably lower than that of organisms growing aerobically. Streptidine can partially reverse the growth inhibitory effect of streptomycin. During the period in which growth becomes inhibited by streptomycin, the rates of incorporation of 14C-labelled precursors into the major cell constituents, and of synthesis of nucleic acids, are reduced simultaneously, and no large changes occur in the total quantities of amino acids or 260 mμ-absorbing substances in the metabolic pool. During this period the rate of metabolism of glucose via the Embden-Meyerhof pathway is decreased, but there is no change in the proportion of the total glucose oxidized which is metabolized via a C1-preferential oxidation. The Q o2 value for oxidation of glucose by organisms harvested when inhibition of growth by streptomycin is first detectable is lower, by about 20%, than that of normal organisms, and falls to c. 30% of normal when growth is fully inhibited. At this time the Q o2 values for oxidation of glycerol, lactate and formate are also reduced, by 40–80%. These effects appear to be specific to organisms whose growth is inhibited by streptomycin.
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