Mapping of prophage P22 in Salmonella typhimurium.

Abstract

Mutants resistant to phage P22 by virtue of roughness, due to mutation at rouB, were obtained in P22-lysogenic and nonlysogenic forms of two genetically marked lines of Salmonella typhimurium strain LT2. Crosses permuted in respect of the lysogeny or nonlysogeny of the rough metA tryB donor and of the rough adeC proA ile str-r acceptor line were then made, using the colicine factors colI and colE1 to obtain conjugation and recombination. When the donor was P22-lysogenic and the acceptor was nonlysogenic there was a great reduction in the yield of recombinants with the linked azi, pro, and gal alleles of the donor. In the cross of the nonlysogenic donor to the lysogenic acceptor the yield of recombinants with the pro+ donor allele was normal. In this cross all the recombinant clones with the pro+ allele from the donor were either nonlysogenic or mixed in respect of lysogeny, though homogeneous in respect of all other segregating characters. By contrast only one of 54 recombinants with the ile+, but not the pro+, donor allele was nonlysogenic. The results suggest that in lysogenic S. typhimurium strain LT2 prophage P22 is always or nearly always located on or in the chromosome very close to proA.