Towards single-copy gene expression systems making gene cloning physiologically relevant: Lambda InCh, a simple Escherichia coli plasmid-chromosome shuttle system

We describe a simple system for reversible, stable integration of plasmid-b orne genes into the Escherichia coli chromosome. Most ordinary E. coli stra ins and a variety of pBR322-derived ampicillin-resistant plasmids can be us ed. A single genetic element, a lambda phage, is the only specialized vecto r required. The resultant strains have a single copy of the plasmid fragmen t inserted stably at the lambda attachment site on the chromosome, with nea rly the entire lambda genome deleted.