sentence: A CD1492 CD2492 double mutant exhibited significantly increased sporulation compared to the 630 Δ erm parent ( Fig. 6A and E ) , and the overexpression of dccA in the CD1492 CD2492 background reduced the sporulation frequency ∼ 3-fold ( Fig. 5E ) , demonstrating that CD1492 and CD2492 are not a required part of the c-di-GMP signaling pathway.We also asked whether c-di-GMP signals through SigD to control C. difficile sporulation .