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

M Higuchi, S Araya, M Higuchi

    Journal of Dental Research
    |March 1, 1976
    PubMed

    Insights

    Plasmid DNA in Streptococcus mutans controls the production of extracellular polysaccharides. Mutants lacking this plasmid DNA produced more soluble polysaccharides and less insoluble glucan and fructan.

    Area of Science:

    • Microbiology
    • Molecular Biology
    • Genetics

    Background:

    • Streptococcus mutans is a key cariogenic bacterium.
    • Extracellular polysaccharides (EPS) play a crucial role in biofilm formation and virulence.
    • The genetic basis for EPS synthesis in S. mutans is not fully understood.

    Purpose of the Study:

    • To investigate the role of plasmid DNA in S. mutans.
    • To determine if plasmid DNA is involved in the synthesis of extracellular polysaccharides.

    Main Methods:

    • Buoyant-density equilibrium centrifugation was used to detect plasmid DNA in S. mutans cell lysates.
    • Mutants were generated using chemical agents (EB, acridine orange, SDS) known to eliminate extrachromosomal DNA.
    • Polysaccharide production (soluble and insoluble glucans and fructans) was quantified in parent strains and mutants.

    Main Results:

    • A satellite band of plasmid DNA was detected in wild-type S. mutans strains.
    • Mutants lacking detectable plasmid DNA showed a reduced ability to synthesize insoluble extracellular polysaccharides.
    • These plasmid-deficient mutants produced increased amounts of soluble polysaccharides from sucrose.
    • The defect in insoluble polysaccharide synthesis affected both glucan and fructan formation.

    Conclusions:

    • Plasmid DNA in S. mutans appears to genetically control the enzymes responsible for extracellular insoluble glucan and fructan synthesis.
    • Elimination of plasmid DNA leads to altered polysaccharide profiles, impacting virulence.
    • These findings highlight the importance of plasmids in S. mutans virulence factor production.

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