On the transformation of coliform types, proper and irregular forms

Abstract

Physiological changes have been induced in strains of E. coli I and its irregular forms, using a basal synthetic medium and addition of sodium pyruvate, or glucose, or yeast extract, or peptone. Changes in biochemical patterns, using the IMViC reactions plus growth at 44.5 degrees C, were induced, thus brining transformations between the regular types and irregular forms. Ultra-violet irradiation of E. coli I for 90 seconds may turn it into a methyl-red negative strain, while education of E. coli III for producing acid and gas at 44.5 degrees C was possible. Thus, E. coli I could be transformed to give the same reactions as the untyped form 1 of Geldreich (1966) through U.V. irradiation, while E. coli III may give the biochemical reactions of E. coli I via heat-resistance and training in MacConkey broth. The relationship between regular and irregular coliforms was also verified by phage typing. The results obtained were discussed both qualitatively, using "lytic activity", and quantitatively in terms of "efficiency of plating", especially with sewage-derived phages and irregular coliforms.