Specialized transduction of kanamycin resistance in a Providence strain

Properties of a transducing system with a phage able to transduce a kanamycin-resistance marker of the T compatibility group plasmid R394 at a frequency of 2 times 10(-2)/plaque-forming unit adsorbed are described. The phage was detected in Providence strain P29 transduced to kanamycin resistance by Providence phage PL25 grown on this strain harbouring the R factor. Four P29 transductants, specially selected at the lowest multiplicities of infection of the high frequency transducing (HFT) phage, were defective lysogens. They plated PL25 with an efficiency of I and only one liberated low-titre phage spontaneously or on u.v. induction. The defect in maturation function could be corrected by introduction of a wild PL25 prophage. The transducing phage was serologically frequency was increased by the simultaneous presence of homologous non-transducing phage. Transductants did not transfer the kanamycin-resistance marker by conjugation, and produced kanamycin-sensitive segregants at a moderate rate. These segregants could be transduced to kanamycin resistance by the HFT phage. Irradiation of HFT lysates by u.v. produced an exponential fall in transduction frequency. It was concluded that the defective phage transduced by lysogenization. Kanamycin-resistant transductants could themselves be transduced by streptomycin resistance by PL25 reared on a streptomycin-resistant mutant. Lysogenic transductants produced by the HFT phage did not always liberate HFT phage on u.v. induction. Possible explantations are considered.