Identification and characterization of sporulation-dependent promoters upstream of the enterotoxin gene (cpe) of Clostridium perfringens

Abstract

Three promoter sites (P1, P2, and P3) responsible for the sporulation- associated synthesis of Clostridium perfringens enterotoxin, a common cause of food poisoning in humans and animals, were identified. Nested and internal deletions of the cpe promoter region were made to narrow down the location of promoter elements. To measure the effects of the deletions on the expression of cpe, translational fusions containing the promoter deletions were made with the gusA gene of Escherichia coli, which codes for β-glucuronidase; E. coli-C. perfringens shuttle vectors carrying the fusions were introduced into C. perfringens by electroporation. In addition, in vitro transcription assays were performed with the cpe promoter region as the DNA template for extracts made from sporulating cells. DNA sequences upstream of P1 were similar to consensus SigK-dependent promoters, while P2 and P3 were similar to consensus SigE-dependent promoters. SigE and SigK are sporulation-associated sigma factors known to be active in the mother cell compartment of sporulating cells of Bacillus subtilis, the same compartment in which enterotoxin is synthesized in C. perfringens.