Comparison of glycine enhancement with cefoxitin induction of class 1 beta-lactamase production in Enterobacter cloacae ATCC 13047.

The presence of either glycine or cefoxitin in the growth medium resulted in an increase in the beta-lactamase activity of cultures of Enterobacter cloacae ATCC 13047. Although the beta-lactamases produced as a result of either glycine enhancement or cefoxitin induction were identical there were striking differences in the kinetics of beta-lactamase production. The increased production of beta-lactamase which resulted from enhancement by glycine occurred late in the growth cycle whereas, with cefoxitin induction, the maximum production of beta-lactamase occurred early in logarithmic-phase growth. After the peak activity was reached the beta-lactamase activity appeared to decline with both processes. However, the mechanism of the apparent fall in the intracellular beta-lactamase activity was different with glycine enhancement and cefoxitin induction. In glycine enhanced cultures the fall presumably was due to leakage of intracellular beta-lactamase into the culture medium whereas with cefoxitin induced cultures there was dilution of beta-lactamase activity by bacterial protein derived from an increase in cell numbers after the cessation of induction. High extra-cellular levels of beta-lactamase activity were observed in cultures enhanced by glycine, whereas little beta-lactamase activity was detected in the medium when the cultures were induced by cefoxitin. The findings demonstrate that there are considerable differences between glycine enhancement and cefoxitin induction, but a final mechanism common to both processes exists which results in the production of identical beta-lactamases by E. cloacae ATCC 13047.