SUMMARY: Properties of two transducing systems with phages capable of high frequency transduction (HFT) of streptomycin and sulphonamide resistance markers of the V group plasmid R905, and of these markers plus the kanamycin resistance marker derived from a previously described HFT phage 5006MHFT, are described. Transducing particles of the former phage, named 5006MHFT, were detected using the replica-plate technique in an ultraviolet-induced lysate of strain 5006 transduced to streptomycin and sulphonamide resistance by phage 5006M grown on 5006 carrying R905. Phage 5006MHFT was also detected by the replica-plate technique in ultraviolet-induced lysates of phage 5006MHFT transductants retransduced to ampicillin and kanamycin resistance by phage 5006MHFT. Both phages were serologically identical to the parent phage 5006M. Ultraviolet-induced lysates transduced their markers to 5006 at frequencies of about 5 x 10/plaque-forming unit adsorbed for both the phages. With phage 5006MHFT, this frequency was increased about 10-fold by simultaneous infection of recipients with homologous non-transducing phage, while phage 5006MHFT transductions only underwent a twofold increase. Transductants took about 60 min to express complete resistance to 50 μg streptomycin/ml, and resistance to 1600 μg sulphadiazine/ml was complete within 120 min after phage adsorption. Phage 5006MHFT was slightly more resistant to ultraviolet inactivation of its transducing potential and reasons are given for the belief that transductants of both phages are heterogenote-like. Both phage lysates were also capable of generalized transduction and, like previously described HFT phages, lysates transduced the leucine marker at increased frequencies. Using previously described extra- and intra-species phage hosts, it was found that the phages could transduce in single infection and were defective in the lysogenic conversion function as well as in a maturation step. Possible modes of formation of the HFT particles are discussed.


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