Identification of Escherichia coli strains for the heterologous overexpression of soluble Clostridium difficile exosporium proteins.

Clostridium difficile infections are one of the leading causes of hospital-acquired infections. C. difficile spores are considered the morphotype of transmission and recurrent infection due to its natural spore resistance properties. The outermost spore layer, the exosporium, provides the first contact with the environment and the host. However, molecular biology studies on exosporium proteins are lacking primarily due to difficulties in over-expressing these proteins under soluble conditions. In this work, we have developed a protocol to express soluble exosporium proteins of C. difficile spores in the heterologous Escherichia coli host. We found that the optimum soluble expression conditions may vary between 21, 30 and 37 °C, depending on the protein, and at least CdeC, BclA1 and BclA3, required E. coli strains that provided an oxidative environment such as Shuffle T7. These results will allow further studies with recombinant proteins of the exosporium of C. difficile spores.