The growth kinetics of the wild type and CT::tcdC strains showed no significant differences in various media tested ( Figure 1E and data not shown). In TY broth, which does not contain glucose or added cysteine, the wild type strain and the CT::tcdC strains showed an exponential growth phase in the first 8 hours post inoculation and after 12 hours post inoculation both strains entered into the stationary growth phase ( Figure 1E ). Conventional control PCRs confirmed that the disruption of the tcdC gene had remained intact during our growth curves experiments (data not shown).