ABSTRACT
Abstract Recent findings have greatly increased our understanding of toxin gene regulation in Clostridium. The VirR/VirS two-component regulatory proteins regulate transcription of genes encoding extracellular toxins in Clostridium perfringens. Some genes are directly activated by the VirR response regulator that interacts with the target DNA. In other cases, a VirR/VirS-dependent regulatory RNA is required for gene expression via an as yet unidentified mechanism. The transcription of the enterotoxin gene in C. perfringens appears to be regulated by mother cellspecific sigma factors, o E and σκ, which are present and active only during sporulation. Transcriptional regulation utilizing alternative sigma factors has also been uncovered in recent studies of toxin gene regulation in Clostridium difficile, Clostridium tetani, and Clostridium botulinum. Continued genome sequence determination of Clostridium spp., as well as transcriptome and proteome analyses, will greatly contribute to furthering our understanding of how toxin genes are regulated by various regulators and environmental factors.
