Restricted trandsuction by bacteriophage P22 inSalmonella typhimurium

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Abstract
1. In the transductionpro-401 (×) + some of the transductants are surrounded by several hundred small wild-type satellite colonies; these transductants spontaneously release phage which transducespro-401 to wild-type at high frequency (HFT phage).2. When the HFT phage is used to infectpro-401 at very low multiplicities of infection, most of the transductants are defective lysogens and segregate proline-requiring phage-sensitive derivatives; these transductants are apparently heterogenotes. At higher multiplicities of infection, or with lysogenic recipients, a higher proportion of satellited transductants is found.3. The HFT phage preparations transduce only the proline region of the donor genome.4. The existence is inferred of a defective P22 particle specifically incorporating the proline region of theSalmonellachromosome; these defective particles can establish themselves as prophage and confer immunity upon the infected cell, but are unable to replicate unless a normal prophage is also present. Satellited transductants are lysogenic both for a normal and defective (proline region carrying) phage, and so on lysis release transducing phage.5. This system is compared with the λdg-galand P1-dl-lacsystems inE. coli.