Characterization of the Gene Encoding the β-Lactamase of the Psychrophilic Marine Bacterium Moritella marina Strain MP-1

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The β-lactamase gene (mbla) of the psychrophilic marine bacterium Moritella marina strain MP-1 was identified in a previously isolated genomic DNA fragment and it was expressed in Escherichia coli cells. The mbla gene encoded a protein consisting of 287 amino acid residues. Its predicted amino acid sequence showed approximately 50% identity with that of a number of class A β-lactamases, especially with that of CARB/PSE type of β-lactamases (carbenicillinases). E. coli transformed with the plasmid containing mbla grew on an amplicillin-containing plate at 37°C but not at 42°C, suggesting that the β-lactamase of this bacterium is heat-labile.