Plasmid DNA satellite bands seen in lysates of Streptococcus mutans that form insoluble extracellular polysaccharides

Abstract

A satellite band of plasmid DNA was seen in cell lysates prepared from two strains of S mutans using buoyant-density equilibrium centrifugation. Mutants, defective in their ability to synthesize insoluble extracellular polysaccharides, showed no detectable satellite DNA band when prepared by the same procedure. These mutants were induced by treatment with EB, acridine orange, or SDS, which are known to be effective agents for the elimination of extrachromosomal genetic inheritance. The derived mutants produced more soluble polysaccharides from sucrose than their parent strains. The decreased ability to synthesize insoluble polysaccharides was related to both glucan and fructan formation. These findings suggest that the plasmid DNA of the S mutans strains genetically controls formation or activity of the enzymes responsible for synthesis of extracellular insoluble glucan or fructan.