STRAIN ALTERATION IN ENTERIC BACTERIA ISOLATED FROM RIVER WATER

Abstract

Enteric bacteria recovered from the Cache la Poudre River and refrigerated for approximately 3 months were observed to form sectored colonies on MacConkey agar subculture. Organisms taken from each sector of the colonies were compared and a wide range of biochemical and serological variation was observed. Selected variant characteristics observed in the pure culture isolates from the sectored colonies were shown to be reproducible with membrane filter U tubes. Further investigation revealed that the agent responsible for the observed variations was submicrobial, survived chloroform and heat (56 C for 30 minutes) treatments, and produced occasional lysis in the non-lactose-fermenting strains. Additional cultures resembling the original variant organisms were recovered from the river but attempts to produce the sectoring phenomenon with these organisms were without success, although numerous sectoring isolates having similar variant characteristics were recovered from the stream.