BLAI AND BLAR1 REGULATE BETA-LACTAMASE AND PBP 2A PRODUCTION IN METHICILLIN-RESISTANT STAPHYLOCOCCUS-AUREUS

For Staphylococcus aureus, it is hypothesized that two genes located u pstream of the beta-lactamase gene, blaZ, are required for the inducib le expression of beta-lactamase. blaR1 is predicted to encode a signal -transducing membrane protein, and blaI is predicted to encode a repre ssor protein. These same two genes may also regulate the production of penicillin-binding protein 2a (PBP 2a), a protein essential for expre ssion of methicillin resistance. To confirm that these two genes encod e products that can control both beta-lactamase and PBP 2a production, blaI, blaR1, and blaZ with a 150-nucleotide deletion at the 3' end we re subcloned from a 30-kb staphylococcal beta-lactamase plasmid and th ree beta-lactamase-negative strains of methicillin-resistant S. aureus were transformed with the recombinant plasmid containing that insert. The production of PBP 2a and a nonfunctional beta-lactamase was detec ted by fluorography and by immunoblots with polyclonal antisera direct ed against each of the proteins. Whereas the parent strains did not pr oduce beta-lactamase and constitutively produced PBP 2a, PBP 2a and a truncated beta-lactamase were now inducible in the transformants. Ther efore, two plasmid-derived genes regulate the production of both PBP 2 a and beta-lactamase.