Synergistic effect of co-expressing d-amino acid oxidase with T7 lysozyme on self-disruption of Escherichia coli cell

Recombinant Escherichia coli with self-disruption characteristic was developed. The cell harbored a d-amino acid oxidase (DAAO) expressing plasmid resulted in an obvious self-disruption. When T7 lysozyme instead of DAAO was used as a lysis gene, no appreciable self-disruption was observed. In the presence of two compatible plasmids, which expressed DAAO and T7 lysozyme, respectively, E. coli BL21(DE3) showed a significant self-disruption. A lysis plasmid containing both inducible DAAO and constitutive T7 lysozyme genes were, therefore, constructed to make the transformed cells self-disrupt more effectively. Green fluorescent protein (GFP), a model target protein, was co-expressed in this self-disruptive E. coli cell. About 60% of the cells were self-disrupted when the lysis genes were induced by isopropyl thiogalactoside (IPTG). The cell disruption efficiency reached to 90% after freeze/thawing treatment.