239. Examples of variation within pure cultures ofStreptococcus cremoris

Abstract

Indications of variability within pure strains of Str. cremoris have been studied.In one strain changes in acid-producing power were made evident by changes in colony form. A variant which failed to ferment lactose but was still susceptible to the specific race of bacteriophage and exhibited the same morphology (after treatment at 37° C.) as the parent culture is described.It was found that variation was well marked within some strains, especially in regard to acid production (or vitality), response to high temperature conditions, power to produce ropiness in milk, and degree of resistance to phage attack.