Molecular cloning and expression of an extracellular nuclease of Serratia marcescens in Escherichia coli

Abstract The gene encoding an extracellular nuclease of Serratia marcescens was cloned in Escherichia coli using the vector pBR322. Transformants were selected by their ability to grow in the presence of ampicillin, and nuclease-positive clones were detected on a commercially available DNase test agar. The production of a nuclease could be detected in recombinant strains and enzyme activity was found in culture supernatants of such strains. Deletion derivatives of the parental recombinant plasmid were constructed to define the region of DNA encoding the expression of the nuclease. The smallest DNA fragment found to produce the nuclease was determined to be 2.2 kb in length, although a somewhat smaller fragment appeared to be partially active.