Identification of a novel locus that regulates expression of toxin genes in Clostridium perfringens.

A novel gene that regulates the alpha-toxin (plc), kappa-toxin (colA), and theta;-toxin (pfoA) genes was identified using toxin-negative mutant strains of Clostridium perfringens. The cloned 3.2-kb fragment contained the virX gene encoding a 51-amino acid polypeptide of unknown function that seemed to be responsible for the activation of toxin genes. The virX knock out mutant of wild-type strain 13 showed a reduced expression of the plc, colA, and pfoA genes, which was complemented by the transformation of the intact virX gene. Deletion and site-directed mutagenesis studies suggested that the virX gene acts as a regulatory RNA rather than as a peptide regulator. The virX locus found in this study might play a part in the signal transduction to regulate toxin production in C. perfringens.