CLOSTRIDIUM-PERFRINGENS UREASE GENES ARE PLASMID-BORNE

Although many bacteria are ureolytic, and in some cases urease acts as a virulence factor, the urease phenotype has not been analyzed in the anaerobic pathogen Clostridium perfringens. In this study, similar to 2% of C. perfringens strains, representing the principal biotypes, we re found to harbor the urease structural genes, ureABC, and these were localized on large plasmids that often encode, in addition, the letha l epsilon or iota toxins or the enterotoxin. This represents the first report of a plasmid-encoded urease in a gram-positive bacterium. The C. perfringens enzyme was highly similar to the ureases of other bacte ria and cross-reacted with antibodies raised against the urease purifi ed from Helicobacter pylori. Urease production was inhibited by urea a nd induced under growth conditions where the availability of nitrogen sources was limiting. To date, this form of regulation has been observ ed only for chromosomal ureABC genes.