S U M M A R YHigh frequency transducing (H FT) phages 5oo6MHFTk and 5006MHFTak for kanamycin or ampicillin plus kanainycin resistance, derived from Proteus nzirabilis strains ~~5 0 0 6 ( R 3 9 4 ) and P M~O O~( R394) respectively, transduced (at low multiplicities of infection, m.0.i.) antibiotic resistance and prototrophy to ~~5 0 0 6 leu-I at high frequency. Simultaneous transduction of these markers occurred at very much lower frequencies. The latter result was correlated with the proportion of multiply-infected bacteria which, due to the great transducing potential of the phage, could register as transductants. Each HFT lysate was thus heterogenous with regard to high frequency transducing phage. Apart from the additional antibiotic resistance marker carried by one phage, no other difference between the two lysates was detected. High segregation frequencies of antibiotic-resistant or prototrophic transductants indicated transduction by lysogenization. Although antibiotic-sensitive segregants of antibiotic-resistant prototrophic transductants occurred at high frequency, no auxotrophic segregants of these transductants were found. This suggests transduction by a double cross-over event in the leucine region. Most transductants, even at low m.o.i., were lysogenically converted to homologous phage non-adsorption as a result of interaction between the transducing phage genome and the resident cryptic prophage. They could, however, be retransduced by appropriate phage lysates; thus, lysogenic conversion to non-adsorption was not absolute. Some prototrophic transductants were non-lysogenic although their segregants liberated low-titre phage. The latter anomaly, and the fact that the leucine marker and anti biotic resistance were not cotransduced, are explained by the mode of integration of the phage into the host chromosome in relation to the resident cryptic prophage and the leucine region.--

Morganocin 174-induced lethality was characterized by one-hit kinetics. Although it induced simultaneous inhibition of deoxyribonucleic acid, ribonucleic acid, and protein syntheses, the most striking effect of morganocin was a rapid reduction of intracellular adenosine 5'-triphosphate to less than 10% of the initial values within 2 min of addition. Accumulation of thymidine, uridine, glutamine, and proline was also inhibited. A gradual efflux of K+ was observed, but the lethal effects of morganocin 174 could not be prevented by maintaining a high K+ or Mg2+ concentration. The Morl74 plasmid codes for an immunity substance that protects cells against the effect of morganocin 174.

SUMMARYAttempts were made to obtain recombinants between the morganocinogenic factor Mor I 74 and R plasmid R772 by transductional techniques. Transduction frequencies of the kanamycin resistance marker of R772 to Proteus mirabilis ~~5 0 0 6 or Providence ~2 9 carrying Mor174 by phages 5006M and PL25, respectively, were I ooo-fold higher than to the corresponding Mor I 74-strains. The frequency of phage PI -mediated transduction of the same marker to Escherichia coli ~6 2 was high and was not affected by the presence of Mor174 in the recipient. Transduction of the kanamycin resistance marker to ~~5 0 0 6 yielded heterogenotelike transductants. Transduction of the same marker to ~~5 0 0 6 with Mor174 as resident resulted in transductants which not only yielded low frequency kanamycin resistance transducing particles on induction but could transfer Mor174 and the transduced marker independently by conjugation. It was suggested that MorI 74 exerted some function in establishing a transductionally shortened R factor. Mor174 also possibly played a role in the separation of the phage component of the transducing particle from the R factor portion. The severed phage genes could then integrate in tandem to a cryptic prophage to render transductants inducible. A phage 5006M lysate of P M~O O~( M O~ I 74R772) produced a cotransductant. This transductant could not, possibly due to more extensive transductional shortening, transfer markers by conjugation. Induction yielded some particles which could cotransduce the markers to ~~5006(P-lac). With assistance of the latter conjugative plasmid, markers of Mor174 and R772 were transferred as a unit by conjugation to strain 562. Phage PI reared on the latter transconjugant cotransduced the genes for MorI 74 activity and kanamycin resistance. Morganocin production by the recombinant equalled that of Mor174.