An Effect of Early Dilution on the Establishment of Lysogeny in Salmonella typhimurium

Abstract

IT is known that the frequency of lysogenic response in a culture of Salmonella typhimurium strain LT2, infected with the temperate bacterio-phage P22, can be influenced by the ratio of phage to bacterium (multiplicity of infection)^1–3, and by modifying the metabolism of the infected cells soon after infection, for example, by the addition of chloramphenicol⁴. With a high multiplicity of infection a high frequency of lysogenic response is obtained. Using a low multiplicity of infection a low lysogenic response results. If these infected cells are exposed to chloramphenicol (25 µgm./ml.) 5 min. after infection and the chloramphenicol removed by dilution 15 min. later, then practically every cell infected becomes lysogenic.