Cloning and expression of the imipenem-hydrolyzing beta-lactamase operon from Pseudomonas maltophilia in Escherichia coli.

The L-1 penicillinase structural gene, blaS, from Pseudomonas maltophilia has been cloned into the vector pACYC184. The pMON01 recombinant plasmid selected by ampicillin resistance carried a 2.6-kilobase Sau3A fragment of P. maltophilia DNA and was confirmed to express L-1 beta-lactamase by comparative isoelectric focusing. A detailed physical map was constructed, and the blaS structural gene was localized with a 17-mer oligonucleotide mixed probe encoding the L-1 N-terminal amino acid sequence. Induction studies confirmed constitutive expression. Isolation of a complete beta-lactamase operon was attempted by construction of a P. maltophilia genomic library into phage lambda 2001. A recombinant phage was selected by DNA hybridization, and the 13.4-kilobase DNA insert was physically mapped and subcloned into plasmid vectors. Expression and L-1 beta-lactamase synthesis were studied in Escherichia coli.