Mutants in the ptlA-H genes of Bordetella pertussis are deficient for pertussis toxin secretion

The nine pll genes (A-I) are required for efficient secretion of pertussis toxin past the outer membrane. Mutations were made in ptlA-H by filling in unique restriction sites, generating in-frame deletions, or inserting a FLA G epitope tag. The mutations were cloned into a suicide shuttle plasmid con taining the ptxptl operon and introduced into the adenylate cyclase locus o f the chromosome of a Bordetella pertussis strain deleted for ptx. The wild -type ptxptl operon restored pertussis toxin expression and secretion. The ptl mutant constructs also restored expression of periplasmic pertussis tox in to the ptx deletion strain but the mutants had a statistically significa nt decrease in secretion of pertussis toxin of between 5- to 35-fold, sugge sting all of the prl genes must be intact for efficient pertussis toxin sec retion. The mutations were also introduced into the adenylate cyclase locus of a wild-type ptxptl strain, resulting in a ptl diploid strain. The PtlC, PtlD, PtlE, PtlF, PtlG and PtlH mutants exerted dominance over the wild-ty pe allele. (C) 1999 Federation of European Microbiological Societies. Publi shed by Elsevier Science B.V. All rights reserved.