Growth and Toxin Synthesis in Batch and Chemostat Cultures of Corynebacterium Diphtheriae

SUMMARY Toxin synthesis in restricted-iron batch cultures of Corynebacterium diphtheriae cn2000 (a pw8 s pd strain) was proportional to the bacterial mass above a minimum bacterial concentration. During glucose-limited growth 0·30 g. toxin was released/g. bacterial protein synthesized. In excess of glucose 0·06 g. toxin was released/g. bacterial protein synthesized. Toxin release in glucose-limited continuous cultures followed similar kinetics to the batch cultures. Iron in the restricted-iron medium, 6 μg. atom/l., limited the quantities of iron taken up by the bacteria and of three iron-containing enzymes, but did not restrict bacterial concentration over the range 2·0–4·5 mg. bacterial protein/ml. The addition of 90 μg. atom Fe/l. to a restricted-iron culture rapidly inhibited toxin release.