Molecular Characterization of a Mutation Affecting the Amount of Streptococcus pneumoniae Penicillin-Binding Protein 3

We have studied the molecular structure of the gene for the penicillin binding protein (PBP 3) of the Streptococcus pneumoniae wild-type strain and a laboratory mutant strain that exhibits a reduced amount of this protein on PBP gels. This mutation affects cefotaxime resistance when transferred into resistant strains. We have sequenced the PBP3 gene, dacA, and upstream regions from the wild-type isogenic strain and the laboratory mutant. We show that a deletion of one base-pair in the upstream sequence of this gene account for the phenotype by decreasing the amount of PBP3.