Fig. 4.
Kinetic analysis of progesterone-induced inhibition of C. difficile spore germination. Germination rates were calculated from the linear segment of optical density changes over time. (A) Lineweaver-Burk plots of C. difficile spore germination at various concentrations of taurocholate (6, 8, 10, and 12 mM) and 0.05 (○), 0.1 (●), 0.2 (▵), and 0.4 (▴) mM progesterone concentrations. (B) A replot of slopes from Lineweaver-Burk plots versus progesterone concentrations was fitted to a straight line and yielded a Ki of 0.045 mM for progesterone binding. (C) Dixon plot of C. difficile spore germination at various concentrations of progesterone (0.05, 0.1, 0.2, and 0.4 mM) and 6 (○), 8 (●), 10 (▵), and 12 (▴) mM taurocholate.