STUDIES ON BACTERIAL REDUCING ACTIVITY IN RELATION TO AGE OF CULTURE

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Abstract
The reducing activity of 4-nr. and 18-hr. cells of a strain of Escherichia coli toward 2,3,5-triphenyltetrazolium chloride (TTC) was studied under various environmental conditions. A linear relationship was found to exist between the number of bacteria and TTC reduction. An appreciable lag, however, was encountered with low bacterial concns. The opt. pH of the reaction was about 7.5 for young cells and 8.5 for old cells. For old cells a 1% concn. of NaCl was optimal in TTC reduction. In the complete absence of the salt no TTC was reduced during the course of the expts. Young cells, on the other hand, reached their opt. activity in the absence or at low concns. of NaCl. Concns. of the salt higher than 1% exerted a strongly inhibitory effect on them. Exposure of bacterial suspensions to temps. of 46 to 56[degree]C for 10 min. caused a far more rapid decline in the reducing activity of young cells than of old cells without affecting cell viability in the same way. Several chemical substances were allowed to act on the bacteria. Young cells proved to be more susceptible than old cells to the action of aureomycin, Na iodoacetate, quinone, and 2,4-dinitrophenol. The last compound effected a marked decrease in reducing activity without causing a proportionate loss in cell viability.