Abortive infection of Escherichia coli F+ cells by bacteriophage T7 requires ribosomal misreading

The use of different precisely mapped T3/T7 recombinants strengthens the conclusion that abortive infection by T7 of F plasmid-carrying cells is due to the nucleotide sequence at the end of the T7 gene 1. Furthermore, we demonstrate that the exclusion requires suppression of ochre stop codons, a phenomenon that occurs with low frequency in wild-type cells due to ribosomal misreading. The introduction of rspL mutations in which ribosomal misreading is reduced alleviates the exclusion and the presence of ochre tRNA suppressors increases its severity.