Triornithine-resistant Strains of Escherichia coli

Triornithine-resistant (TOR) mutants were isolated from several strains of Escherichia coli K-12. All of the mutants were found to be oligopeptide transport-deficient (Opp-). The dipeptide transport system (or systems) was not altered. The rate of growth of these mutants, the morphology of the cells and their colonies and the sensitivity to the phages T1, T4, P1, and φ80 were similar to the parental strains, indicating no dramatic changes at the cell envelope. All Opp- mutants tested showed 98% linkage to trp in sexual recombination, and 80 to 95% P1-mediated co-transduction frequencies. The opp gene is therefore the closest marker to the trp operon. A mutant with a deletion in the region att φ80, tonB, trp still contained the opp gene (or genes), indicating its appearance on the cysB side of the trp operon.