Studies on Bacterial Populations in Solutions of Phenols

Abstract

Abstract The shape of time-survivor curves for E. coli suspended in aqueous solutions of benzylchlorophenol depends on the concentration of the bactericide. In some concentrations the last survivors exhibit unexpected multiplication. The death of the organisms is accompanied by the release of cell-constituents having an ultra-violet absorption maximum at 260 mμ. Growth occurred when E. coli exudate was added to aqueous suspensions of E. coli whereas in its absence the organisms died. The numbers of viable organisms depended upon the concentration of the added cell exudate. The fate of the last survivors of a suspension of E. coli in benzylchlorophenol solution was controlled by re-suspending them in components of the reaction mixture. Removal of cell-exudate produced rapid death and the removal of bactericide led to multiplication of the organisms. It is concluded that cell exudate constituted the nutrient substrate for multiplication of last survivors in an initially bactericidal system. The theories of disinfection and the influence of cell exudate upon the shape of time-survivor curves are discussed.