Behavior of Coliphage Lambda in Hybrids Between Escherichia coli and Salmonella

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RESUMO

Salmonella typhosa hybrids able to adsorb lambda were obtained by mating S. typhosa recipients with Escherichia coli K-12 donors. After adsorption of wild-type λ to these S. typhosa hybrids, no plaques or infective centers could be detected. E. coli K-12 gal+ genes carried by the defective phage λdg were transduced to S. typhosa hybrids with HFT lysates derived from E. coli heterogenotes. The lysogenic state which resulted in the S. typhosa hybrids after gal+ transduction differed from that of E. coli. Ability to produce λ, initially present, was permanently segregated by transductants of the S. typhosa hybrid. S. typhosa lysogens did not lyse upon treatment for phage induction with mitomycin C, ultraviolet light, or heat in the case of thermoinducible λ. A further difference in the behavior of λ in Salmonella hybrids was the absence of zygotic induction of the prophage when transferred from E. coli K-12 donors to S. typhosa. A new λ mutant class, capable of forming plaques on S. typhosa hybrids refractory to wild-type λ, was isolated at low frequency by plating λ on S. typhosa hybrid WR4254. Such mutants have been designated as λsx, and a mutant allele of λsx was located between the P and Q genes of the λ chromosome. Plaques were formed also on the S. typhosa hybrid host with a series of λi21 hybrid phages which contain the N gene of phage 21. The significance of these results in terms of Salmonella species as hosts for λ is discussed.

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