DNA restriction and modification systems in Salmonella - III. SP, a Salmonella potsdam system allelic to the SB system in Salmonella typhimurium

By screening 42 Salmonella strains with P3, a temperate bacteriophage with an unusually wide host range, five new DNA restriction and modification systems (R-M systems) were identified in five different serotypes in Kauffmann-White group C. One of these systems, SP, in a Pl-sensitive strain of S. potsdam, was analyzed genetically by Pl transduction methods in which SP was transferred into S. typhimurium and E. coli/S. typhimurium hybrids. It was found that the genes of the SP system were allelic and functionally homologous to the genes of the SB system of S. typhimurium.