Altered linkage values in phage P22--mediated transduction caused by distant deletions or insertions in donor chromosomes.

The effects of distant deletions or insertions in the Salmonella typhimurium donor strains on P22--mediated cotransducibility of genetic markers was studied. We found that deletions of histidine operon, unit 44 of the chromosome map, changed the linkage of markers purF and aroC (unit 49) and pyrF and trpA (unit 34). They did not change the linkage of more distant markers pyrE and cysE. The effect of three types of insertions was examined. The donor strains carried F factor, Tn10 transposon or pi-his duplication inserted close to histidine operon. These insertions caused alteration of purF-aroC linkage while pyrF-trpA cotransduction values were not affected. These data show that the effect of the chromosome rearrangements extends to at least 5% of S. typhimurium chromosome length and may reach as much as 10% of it. Our results are in agreement with the model of Chelala and Margolin (1974) concerning formation of transduction particles. They indicate that the cotransducibility changes caused by deletions or insertions extent further than it might have been expected from previous reports.