Heterogeneity of Cultures of Escherichia coli B/r

Abstract

A LARGE amount of the recent literature in radiation bacteriology and allied fields is concerned with the detailed behaviour of cultures labelled Escherichia coli B and Escherichia coli B/r. E. coli B is a bacterial strain that has been maintained for many years, mainly in laboratories concerned with bacteriophage synthesis and behaviour. It is characterized by its unusual sensitivity to several deleterious agents, including the T series of coli bacteriophages. E. coli B/r is one of a large group of mutants selected from E. coli B after irradiation with ultra-violet light. Witkin carefully defined B/r and distinguished it from B and other ultra-violet-selected mutants of B ^1,2. E. coli B/r was characterized by, among other things, its enhanced resistance to ultra-violet light, X-rays, penicillin, and sodium sulphathiazole. Furthermore, the snake-like forms found with very high frequency in B cultures irradiated with ultra-violet were found only occasionally in B/r.