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A plasmid in Streptococcus pneumoniae.

M D Smith, W R Guild

    Journal of Bacteriology
    |February 1, 1979
    PubMed
    Summary
    This summary is machine-generated.

    Researchers detected plasmid deoxyribonucleic acid (DNA) in specific Streptococcus pneumoniae lab strains. These strains contain a 2.0-megadalton plasmid (pDP1), but its function remains unknown.

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    Area of Science:

    • Microbiology
    • Molecular Biology
    • Genetics

    Background:

    • Streptococcus pneumoniae is a significant human pathogen.
    • Plasmids are extrachromosomal DNA elements that can confer advantageous traits.
    • The presence and role of plasmids in S. pneumoniae laboratory strains are not fully characterized.

    Purpose of the Study:

    • To investigate the presence and characteristics of plasmid DNA in specific laboratory strains of Streptococcus pneumoniae.
    • To determine if plasmid presence correlates with any observable phenotype or antibiotic resistance.

    Main Methods:

    • Plasmid DNA extraction from Streptococcus pneumoniae strains.
    • Agarose gel electrophoresis to analyze plasmid size and quantity.
    • Comparison of plasmid profiles across related laboratory and clinical isolates.

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    Main Results:

    • Three related laboratory strains (D39S, R36, R36NC) were found to contain at least two copies of a 2.0-megadalton plasmid (pDP1) per cell.
    • A larger plasmid, approximately twice the size of pDP1, was also detected in low quantities in these strains.
    • Neither plasmid was detected in four related strains or a drug-resistant clinical isolate.
    • Plasmid yield was not increased by chloramphenicol treatment.
    • No specific phenotype was associated with the presence of pDP1.

    Conclusions:

    • Specific laboratory strains of Streptococcus pneumoniae harbor distinct plasmids, including a prevalent 2.0-megadalton plasmid (pDP1).
    • The presence of these plasmids does not appear to confer a selectable advantage or be linked to antibiotic resistance in the studied strains.
    • Further research is needed to elucidate the function and evolutionary significance of pDP1 in S. pneumoniae.