Induction of Lysogenic Bacteria as a Method of detecting Potential Antitumour Agents

Abstract

IT is known that certain antitumour agents are capable of inducing lysogenic bacteria. Thus, Jacob¹showed that nitrogen mustard had this property, Gots et al.²reported the same for azaserine, and Otsuji et al.³for mitomycin C. It was thought that this property might afford a relatively simple, rapid and convenient method of detecting potential antitumour agents produced by micro-organisms and might also serve as a suitable assay for following extraction procedures. Accordingly, a quantitative method of measuring the induction of λ phage in E. colistrain K₁₂has been worked out. It consists essentially of inducing a young culture of bacterial cells in M9 medium⁴for a period of 1 h with the agent and growing the induced cells in nutrient broth for 2¼ h. Phage counts are then done on plates seeded with the indicator strain E. coli, W3001. At the same time, counts are made of the bacteria since it has been found that, when assaying broths which are rich in nutrient materials, growth of the lysogenic strain can lead to increased phage titres and confuse the results of the test. From the results, the induction index, which is the ratio of phage count to bacterial count, is calculated.