Factors affecting microcin E492 production.

The production of the antibiotic polypeptide microcin E492 by Klebsiella pneumoniae RYC492 has been studied in respect to the composition of the culture medium. The nature of both the carbon and nitrogen sources had a dramatic effect on the levels of the microcin detected in the supernants of the liquid cultures. Gluconeogenic precursors such as lactate or citrate led to microcin titers 10 to 100 fold higher than those obtained with glucose. However, neither glycerol nor cAMP stimulated the production, ruling out a typical type of catabolic repression by glucose. Limitation of growth by phosphate or nitrogen led to a marked decrease in production. Treatment with mitomycin C did not result in an enhancement of microcin levels.