Reduced Oxidative Activities in Escherichia coli and Bacillus megaterium in Relation to Other Changes during Inhibition of Growth by Streptomycin

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Abstract
SUMMARY: When the growth of cultures of Bacillus megaterium KM, Escherichia coli B or Bacillus subtilis ceased following addition of streptomycin during the exponential phase of growth, harvested organisms showed oxidative activities on glucose, lactate, pyruvate and succinate which were between 20 and 60 % of those of normal organisms. With E. coli, this reduction in oxidative activity was closely parallel to the decrease in growth rate. During the period in which growth became fully inhibited by streptomycin, the total quantities of amino acids and 260 mμ-absorbing compounds in hot water extracts of E. coli and B. megaterium did not differ significantly from those in normal organisms. Protoplasts could be prepared in normal yield from streptomycin-inhibited organisms of both these species; such protoplasts showed normal stability and had internal osmotic pressures which differed only slightly from normal. From these results it appears unlikely that there was any general breakdown of the permeability barrier of these organisms during inhibition of growth by streptomycin. Lysates of protoplasts from streptomycin-inhibited Bacillus megaterium showed oxidative activities which were also decreased to between 20 % and 45 % of those of lysates from normal organisms. With succinate and malate as substrates this difference appeared to be due predominantly to a considerable decrease in the activity of the sedimentable ‘ghost’ fraction of the lysed protoplasts.