FIG 7.

Effects of oligopeptide transporters on toxin gene expression. (A, B) qRT-PCR analysis of tcdA (A) and tcdB (B) expression in 630Δerm, MC296 (opp), MC301 (app), and MC307 (opp app) grown in 70:30 sporulation medium to OD₆₀₀s of 0.5 (log phase) and 1.0 (start of stationary phase; T₀) and 2, 4, or 8 h after T₀ (T₂, T₄, and T₈), as described in Materials and Methods. The means and standard errors of the means of four biological replicates are shown. *, P ≤ 0.05 by a two-tailed Student's t test. The key at the bottom right applies to panels A and B. (C) qRT-PCR analysis of tcdA, tcdB, sigE, and sinR gene expression in cecal contents from hamsters infected with either 630Δerm or MC307 (opp app). The means and standard errors of the means of samples from at least 10 animals per strain are shown. *, P ≤ 0.05 by a two-tailed Student's t test.