Distribution of Numbers of Mutant Bacteria in Replicate Cultures

Abstract

SINCE the publication by Lea and Coulson¹ of the expected distributions of numbers of bacterial mutants in replicate cultures, there has been only one limited attempt to compare this theory with experimental observations. Armitage² has shown that Lea and Coulson's unmodified theory will not allow a description of the pattern of mutants in Escherichia coli resistant^3,4 to phage T1. In the literature a number of other examples are available for comparison. Experiments on mutation to resistance to ultra-violet radiation⁵ and to histidine independence⁶ in E. coli can be shown to give distributions of mutants which, like those to phage resistance, do not agree with the distributions predicted by Lea and Coulson. On the other hand, mutations to penicillin resistance in Staphylococcus aureus⁷, to tryptophane independence in Eberthella typhosa⁸, and to streptomycin resistance in E. coli⁹, give distributions fitting the theoretical one.