Isolation of Salmonella typhimurium cys genes by transduction with a library of recombinant plasmids packaged in bacteriophage P22HT capsids.

We have prepared a library of Salmonella typhimurium genomic fragments cloned in pBR322 and packaged in P22HT capsids. Plasmids carrying 24 of 26 specific genes searched for were isolated by transduction at frequencies of 1 to 344 per 10(6) plasmid transductants. All 11 known genes of the cysteine regulon were isolated from this library, including cysK, which we had previously been unable to clone in a recombinant plasmid with an Escherichia coli host. This library provides a simple and rapid method for isolating most S. typhimurium genes by using S. typhimurium itself as a host and should be particularly useful for cloning genes that might be deleterious to E. coli.