The Escherichia coli structural gene for DNA polymerase I was inserted into Salmonella typhimurium chromosome by conjugal transfer. The genetic analysis of P1-mediated transduction of obtained hybrid showed that polA gene is located in it between metE and rha loci and is cotransduced with metE (about 50%) and rha (12%). The phenotypic properties of polA1 hybrid E. coliXS. typhimurium concerning UV-MMS-NG and gamma-ray sensitivity are similar to the polA1 mutants of E. coli.