Bacteria, Dissociation of

one of the manifestations of variability of microorganisms as a result of which bacteria that form large, smooth, shiny colonies on solid nutrient media and are usually designated as S forms (“smooth”) give rise to mutants or R forms (“rough”) that form dull, wrinkled colonies. Bacterial dissociation may occur spontaneously or under the influence of physical or chemical factors. Many physiological, biochemical, and immunological properties of a culture change in the course of bacterial dissociation. Therefore, the wrinkled forms of pathogenic bacteria are not used to make vaccines.