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Dispensable genes and foreign DNA in Streptococcus mutans
Janet C Waterhouse1, Roy R B Russell1
1Oral Biology, School of Dental Sciences, University of Newcastle, Newcastle upon Tyne NE2 4BW, UK.
Microbiology (Reading, England)
|June 1, 2006
Summary
Streptococcus mutans strains exhibit significant genomic variation, with dispensable genes widely distributed through horizontal gene transfer, indicating a core and dispensable genome structure.
Area of Science:
- Microbiology
- Genomics
- Molecular Biology
Background:
- Streptococcus mutans strains display variable properties like sugar utilization and mutacin production.
- Genomic sequencing of S. mutans UA159 revealed putative genomic islands and insertion-sequence elements.
- These elements suggest the presence of foreign DNA and genomic plasticity in S. mutans.
Purpose of the Study:
- To investigate genomic variation among diverse Streptococcus mutans strains.
- To identify the presence and distribution of insertion-sequence elements and genomic islands.
- To understand the mechanisms driving genomic diversity in S. mutans.
Main Methods:
- Designing PCR primers based on the S. mutans UA159 genome sequence.
- Analyzing a collection of 39 S. mutans strains isolated globally over 40 years.
- Investigating insertion/deletion events and the presence of foreign DNA.
Main Results:
- Extensive genomic differences were detected among the analyzed S. mutans strains.
- Similar insertion and deletion events were observed in strains from different origins.
- In two cases, foreign DNA insertion appeared to have displaced native S. mutans genes.
- Deletions in sugar metabolism genes were also noted.
Conclusions:
- Streptococcus mutans possesses a core genome and a dispensable genome.
- Dispensable genes are widely distributed across strains, likely via horizontal gene transfer.
- Genomic plasticity and horizontal gene transfer contribute significantly to S. mutans evolution and diversity.