Selection of bacterial pac sites recognized by Salmonella phage P22.

A gene library of chromosomal PstI fragments from Salmonella typhimurium strain DB5575 has been established. By means of phage P22 mediated transduction, ten different clones which contained inserts that promoted plasmid transduction were selected out of a total of about 7,000 clones. Seven of these clones carried inserts that stimulated transduction independently of general and int-promoted recombination and were interpreted as carrying pac analogous signals. The remaining three clones carried inserts that promoted transduction under recombination proficient conditions, whereas transduction occurred at reduced rate in the absence of recombination. These were believed to have short regions of homology with P22 DNA.