Escherichia coli strains were routinely grown in Luria-Bertani broth or plates, supplemented with appropriate antibiotics. Chloramphenicol was used at a final concentration of 20 mg/mL for agar plates and 10 mg/mL for liquid cultures. Ampicillin was used at a final concentration of 100 mg/mL. Kanamycin was used at a final concentration of 20 mg/mL. Cloning was carried out using E. coli DH5a, overexpression was performed in E. coli Rosetta(DE3) pLysS (Novagen). C. difficile strains were grown in a glucose-free trypton-yeast based medium (TTY; 3% w/v bactotrypton (BD), 2% yeast extract (Fluka), 0.1% w/v thioglycollate (Sigma) pH 7.4), supplemented with 20 mg/mL of lincomycin when appropriate, or on CLO or TSS plates (Biomerieux).