Intra-species tranduction with Proteus mirabilis high frequency transducing phages

The properties of three additional Proteus mirabilis hosts for the high frequency transducing (HET) phages 5006MHFTkappa and 5006MHFTak are described. The phages transduce resistance to kanamycin and to ampicillin plus kanamycin, respectively, and were produced by ultraviolet induction of derivatives of P. mirabilis strain PM5006. Strain PM804 could not be shown to adsorb the phages although it yielded a few transductants. All transductants, even those produced at low multiplicities of phage input were lysogenic and segregated markers at high frequency. Ultraviolet induced phage lysates of these transductants transduced PM804 at higher frequencies and PM5006 at lower frequencies than the original phages. Strain PM804 or its derivatives did not adsorb phage from these lysates. Tranmission experiments through PM5006 of phage in the transductant lysates confirmed that PM804 had a host-controlled modification system which modified HFT phage from PM5006. That PM804 also possessed a restriction system was inferred from the greater numbers of transductants obtained with page which bore a compatible modification pattern. Strain N and a restrictionless mutant of it named NHI, adsorbed the HET phages avidly and failed to modify their host range. Transduction frequencies of the phage markers were about 10(-4)/p.f.u. adsorbed to strain NHI and only about tenfold lower to strain N which did not plate the phages. Tranductants also had the features of heterogenotes and those obtained at low multiplicites of infection were non-lysogenic. The latter transductants adsorbed homolgous phage while NHI transductants also plated the HFT lysates. Strain NHI, lysogenized by the parent phage 5006M, did not adsorb the HFT phages. These findings suggest that the HFT phages were most likely defective for lysogenic conversion to homologous phage non-adsorption. The postulated restriction enzymes of PM804 and strain N could not be shown to be thermolabile.