Carbon Dioxide and Bacterial Toxin Production

Conclusions

1. Cahon dioxide plays an important role in toxin production, by preventing the destruction of the toxin, once it is formed. This is probably done by regulating the reaction of the medium.

2. It is possible to control the reaction of C. diphtheriae cultures of an initial pH 7.4 to 7.6 by passing an atmosphere containing from 3 to 5 per cent CO₂ over them. By this procedure an abundant supply of oxygen is maintained.

3. Increased CO₂ tension also prevents the rapid destruction of the organisms present after the period of maximum growth, probably by controlling the reaction of the medium.

4. “Peptones” high in proteose content are apparently necessary for toxin production for other reasons than their buffering action.

5. More abundant growth was obtained with Difco-Proteose Peptone, either with or without increased carbon dioxide tension, than with Difco-Bacto Peptone.

6. No appreciable amounts of toxin were found during the period of most active growth, which is the period of decrease in amino acid supply. On the other hand, it seems to be formed after the period of maximum growth, and during time of increase of amino acid content.

7. These tests should help to explain the irregular results obtained in the production of diphtheria toxin when cultures of diphtheria organisms are grown under ordinary conditions.

This is a preliminary report.