Clxx. Oxidation-reduction Potentials of Pneumococcus Cultures. I. by Leslie

THE oxidation-reduction potentials established in cultures during the growth of various bacteria under different conditions have been described in previous communications. By extending these studies to other bacteria it is hoped to reveal the general effects of cultural conditions and the individual differences between different organisms. Serum proteins have an inhibiting effect on the establishment of reducing conditions with each organism studied. The presence of glucose has the same general effect in each case but with individual differences. In aerobic broth cultures haemolytic streptococci [Hewitt, 1930, 1] may be sharply differentiated from C. diphtheriae [1930, 2] and staphylococci [1930, 3] by the rise in potential with the first named organisms after the logarithmic phase of growth. With the two latter organisms the potential remains at a low level long after the cessation of active proliferation. A similar difference is observed in aerated broth cultures. With streptococci the potential falls very much less when the cultures are aerated and, after the logarithmic phase of growth, the potential rises rapidly until the high level corresponding to peroxide formation is reached. In the case of diphtheria and staphylococcal cultures aeration has relatively little effect on the level of reduction potential reached, and the potential after the logarithmic phase of multiplication does not rise to a high oxidising level. Since peroxide formation occurs in streptococcal cultures but not in diphtheria or staphylococcal cultures, it is possible that the general character of the potential-time curves may be due to the ability or inability on the part of the organisms to form peroxide. Since the pneumococcus is a peroxide-forming organism it should behave similarly to the streptococcus and differently from C. diphtheriae and Staphylococcus aureus. METHODS.