C. difficile Spo0A-DBD Shows Similar Specificity as B. subtilis Spo0A-DBD Next, we examined the conservation of the DNA binding domain of Spo0A (Spo0A-DBD) between B. subtilis and C. difficile. In B. subtilis amino acid residues contacting the backbone of the DNA and interacting with specific residues of the Spo0A binding sequence have been defined [13] . We found that all these residues were conserved in the C. difficile protein sequence (Fig. 2B) , indicating that the protein likely recognizes a similar motif.