Control mechanisms operative in a natural microbial population selected for its ability to degrade L-lysine. I. Effect of glucose in batch systems.

A natural microbial population was selected in a medium containing L-lysine as the sole carbon source and ammonia as a nitrogen source. Cells were harvested from a batch-operated fermentor containing lysine and were grown through one transfer on lysine, glucose, or a mixture of lysine and glucose. By comparing the substrate removal rates and enzymatic capabilities of the cells, it was determined that the inducible enzyme system responsible for lysine degradation was subject to catabolic repression. Inhibition of the activity of preformed enzyme(s) played only a minor role. Preinduction by lysine offered only a small degree of protection against repression. The removal of ammonia nitrogen from the system did not overcome the effect of glucose.