FIG. 1.

Expression of β-lactamase during development. DZF1 cells were plated for development on CF GelGro plates as described in Materials and Methods. Cells were harvested from the plates every hour, lysed, and assayed for β-lactamase activity with cephaloridine as a substrate for the enzyme. Specific activity of the enzyme based upon protein concentrations determined by the bicinchoninic acid assay is reported. The experiment was performed several times, and the results of a typical experiment are shown. (A) Specific activity of β-lactamase during development at 34°C. (B) Specific activity of β-lactamase during development at 28°C.