ACTIVITY OF CHI RECOMBINATIONAL HOTSPOTS IN SALMONELLA TYPHIMURIUM

Gerald R. Smith ¹, Christine M. Roberts ¹, and Dennis W. Schultz ¹

¹ Fred Hutchinson Cancer Research Center, 1124 Columbia Street, Seattle, Washington 98104

Chi sites have previously been shown to stimulate homologous recombination by the Escherichia coli RecBC pathway. To test the activity of Chi in another organism, bacteriophage crosses were carried out in Salmonella typhimurium strains bearing the E. coli receptor protein. Chi is active in these crosses in S. typhimurium, but is less active than in the same crosses carried out in E. coli. The lower Chi activity in S. typhimurium appears to be intrinsic to the S. typhimurium RecBC enzyme, since the Chi activity in E. coli-S. typhimurium hybrids depends on the species of origin of their RecBC enzyme. For these studies we constructed an F' factor and a pBR322-derived plasmid carrying the thyA⁺ recC⁺ recB⁺ argA⁺ region of the S. typhimurium chromosome.