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Molecular, functional, and evolutionary analysis of sequences specific to Salmonella
E A Groisman1, M A Sturmoski, F R Solomon
1Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO 63110.
Summary
Specific Salmonella DNA fragments were analyzed to understand species differentiation. Most fragments showed unique chromosomal positions, with some suggesting horizontal gene transfer, but none impacted virulence in mice.
Area of Science:
- Microbiology
- Genomics
- Bacterial Pathogenesis
Background:
- Salmonellae are linked to numerous diseases, with species-specific DNA sequences suspected in virulence.
- Understanding genetic differences is key to differentiating bacterial species.
Purpose of the Study:
- To identify molecular, genetic, and phenotypic traits distinguishing Salmonella species.
- To investigate the evolutionary origins and functional roles of Salmonella-specific DNA fragments.
Main Methods:
- Analysis of five cloned DNA fragments specific to Salmonella.
- Chromosomal mapping and G+C content determination of DNA fragments.
- Nucleotide sequencing of a fragment with atypical base composition.
- Phenotypic characterization of deletion strains (>120 traits) and virulence testing in mice.
Main Results:
- Most DNA fragments mapped to unique chromosomal locations, suggesting independent evolution.
- Three fragments had lower G+C content than the Salmonella genome, indicating horizontal gene transfer.
- A sequenced fragment contained a gene similar to LysR transcriptional regulators.
- Deletion strains exhibited wild-type behavior in >120 phenotypic tests and mouse virulence assays.
Conclusions:
- The analyzed Salmonella-specific DNA fragments represent independent evolutionary events, with some acquired via horizontal gene transfer.
- The investigated fragment, despite its unique origin, did not confer significant phenotypic differences or affect virulence in the tested models.