Fig. 1. Strain LC693 efficiently sporulates.

C. difficile strains were grown in 70:30 liquid sporulation medium and assayed for spore formation after 24 h of incubation. a Sporulation frequencies were plotted from direct enumeration of spores and vegetative cells in micrographs (data not shown). b Sporulation frequency determined by ethanol inactivation of vegetative cells. The means ± standard deviation of the mean from three biological replicates are shown. Student’s t-test was used to assess significance; ns not significant; *p < 0.05