Gene Order and Co-Transduction in the leu-ara-fol-pyrA Region of the Salmonella typhimurium Linkage Map

Abstract

The gene order and orientation in the leu-pyrA region of the Salmonella typhimurium linkage map was established by phage P22-mediated transductions. The gene order, in counterclockwise orientation, is leuO-leuA-leuB-leuC-leuD-ara-fol-pyrA . The fol locus is co-transducible with either the ara and leu loci or the pyrA locus, whereas no co-transduction for the ara and pyrA loci can be found.

Evolution of a New Gene Substituting for the leuD Gene of Salmonella typhimurium : Characterization of supQ Mutations

“…In general, lower co-transduction frequencies were found when the selected marker was Leu+ (i.e., selection for integration of the supQ mutant allele) than when the selected marker was Pro+. Such differences in co-transduction frequencies, depending on the selection of markers, have been reported previously (7,13). They might indicate a nonrandom production of transducing particles.…”

“…The characterization of a large number of independent supQ mutations had shown that on July 31, 2020 by guest http://jb.asm.org/ Downloaded from they can be point mutations (AP mutagenesis) or deletions, and that their chromosomal location varies significantly (10.5 to 99.9% co-transduction with proA575). Comparing these cotransduction frequencies with values that have been reported for the leu-ara-pyrA (7,9) or trp-cysB region (13), and considering a model for general random transduction (7), one can estimate that a co-transduction frequency of 10% corresponds to a distance of approximately 20 genes (60% of the length of a transducing particle). Regardless of the accuracy of these estimates, it seems untenable that all supQ mutations are mutations within one gene.…”

“…Phage-sensitive (i.e., nonlysogenic) recombinant strains were constructed by transductions with an integration-negative mutant of P22, int4 (15). The construction of recombinant strains, integrating specific leuD mutations into the genome of different complex strains, utilized the fol marker (conferring resistance to trimethoprim), which is co-transducible with the ara and leu operon (7).…”

Salmonella typhimurium mutants with reduced levels of transfer ribonucleic acid-inhibitable endodeoxyribonucleolytic activity

“…All of the EMS-induced mutations which conferred bright fluorescent phenotypes were cotransducible with the serA (phosphoglycerate dehydrogenase) gene in P22-mediated crosses (data not shown). The average cotransduction frequency of 1.2% corresponds to a distance between serA and these mutations of about 0.85 map unit according to the formula derived by Kemper (10). Mutations in the endA locus of E. coli confer a similar phenotype and are located at a corresponding distance from serA on the E. coli map.…”

“…RNase A, which was pretreated at 800C for10 min to J. BACTERIOL. on July 31, 2020 by guest http://jb.asm.org/ Downloaded from endA MUTANTS OF S. TYPHIMURIUM 175…”