Poisson-like fluctuation patterns of revertants of leucine auxotrophy (leu-500) in Salmonella typhimurium caused by delay in mutant cell division

Occurrence of Leu+ mutants from the Salmonella typhimurium leu-500 strain MA 412 at high frequencies on selective plates indicate that such mutants may be 'directed' or induced. The colonies are also formed within a large range of time periods. The mutants are formed on selective plates and are absent in preceding cultures when subjected to nonselective conditions.