The level of expression of α-toxin by different strains of Clostridium perfringens is dependent on differences in promoter structure and genetic background

The control of expression of the α-toxin gene (cpa or plc) of Clostridium perfringens has been studied in three strains shown to have high (NCTC8237), intermediate (strain 13) and low (NCTC8533) phospholipase C activity in the culture supernatant. The phospholipase C activity was shown to be related to cpa mRNA levels. Primer extension studies were performed to locate the cpa promoter regions in strains NCTC8237 and 13. Differences in promoter sequences could account for the differences in α-toxin production between strains 13 and NCTC8237. In contrast, the differences in α-toxin production between strains NCTC8237 and NCTC8533 were unlikely to be due to promoter differences because the upstream promoter-containing sequences were identical in these strains. The recombinant plasmid carrying the NCTC8237 cpa gene was introduced into strains 13 and NCTC8533. The level of production of the α-toxin was 16-fold higher in strain 13, indicating the presence of strain-dependant regulatory systems.