Xxiii. Oxidation-reduction Potentials of Pneumococcus

IN previous communications the electrode potential behaviour of haemolytic streptococci [Hewitt, 1930, 1], C. diphtheriae [1930, 2], staphylococci [1930, 3] and pneumococci [1930, 4] has been described by the author and it has been shown that the oxidation-reduction potentials established in bacterial cultures depend upon the cultural conditions and upon the organism studied. The potentials developed in streptococcal cultures are roughly similar to those in pneumococcal cultures, but are quite different from those in staphylococcal and C. diphtheriae cultures. Haemolytic streptococci and pneumococci form peroxide in aerated cultures, whilst staphylococci and C. diphtheriae do not, and it is becoming increasingly evident that peroxide formation is an important factor in bacterial behaviour. McLeod and Gordon [1923] classify bacteria on the basis of peroxide formation and account for the phenomenon of anaerobiosis on the grounds of the toxicity of peroxide. In his recent work on the effect of oxidation-reduction conditions on bacterial variation Todd [1930] finds that peroxide may have a selective inhibitory effect on a particular variant and thus peroxide formation may lead to selection of another variant less sensitive to peroxide. In view of the importance of peroxide it is of interest to eliminate its effect and to determine what other differences exist between different bacteria. Addition of catalase to a peroxide-forming organism such as the pneumococcus should inhibit peroxide formation and thus reveal other characteristics in its oxidation-reduction behaviour. In this paper are described the effects of catalase on the electrode potentials developed in pneumococcus cultures.