Abstract
Escherichia coli plasmids carrying a DNA restriction fragment corresponding to the extreme right end of the T7 bacteriophage genome render cells incompetent to support reproduction of wild-type T7. Processing of intracellular concatemeric phage DNA and cell lysis are perturbed by one such plasmid, pRS148. The results are discussed with reference to the possibility that the right end of the T7 genome encodes a lysis-related function.