FIG. 3.

Growth-phase-dependent expression of txeR-gusA and tox-gusA fusions in C. perfringens. C. perfringens cells carrying txeR in trans and gusA fusions to the txeR (A), toxA (B), or toxB (C) promoters were grown anaerobically in TY or TYG medium, and the β-glucuronidase activities of cells at different stages of growth were determined over a period of 72 h. The data have been plotted so as to magnify the expression pattern during the exponential phase of growth and entry into stationary phase by introducing a break in the x axis. The arrows indicate the times at which the cultures left the rapid-exponential-growth phase. The graph inset shows the plot of all data points. Solid circles, TY medium; open circles, TYG medium.