Transduction. Strains were infected with an amount of a P1 lysate grown on a metBΔtet strain sufficient to generate 50-100 transductants in the wild type. Ratios of mutant transductants to wild type transductants were calculated. Means and standard errors of 3-8 crosses are shown. A. RecBCD+ strains. B. Strains in which recBCD is replaced by red.