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Utilization of sialic acid by viridans streptococci
H L Byers1, K A Homer, D Beighton
1Joint Microbiology Research Unit, King's College School of Medicine and Dentistry, Faculty of Clinical Dentistry, London, England.
Journal of Dental Research
|August 1, 1996
Summary
Certain viridans streptococci can use sialic acid as a nutrient, aiding their survival in serious extra-oral infections like endocarditis. This metabolic capability is linked to specific enzymes and distinct end-products compared to glucose metabolism.
Area of Science:
- Microbiology
- Bacterial Metabolism
- Molecular Biology
Background:
- Viridans streptococci are increasingly recognized as causative agents of severe extra-oral diseases, such as endocarditis.
- The metabolic capabilities of these bacteria, particularly their nutrient utilization, are crucial for understanding their pathogenicity.
Purpose of the Study:
- To investigate the hypothesis that sialic acid utilization by viridans streptococci contributes to their proliferation in extra-oral sites.
- To identify the specific species capable of utilizing sialic acid and elucidate the metabolic pathways involved.
Main Methods:
- Tested 15 type strains and 2 clinical isolates of viridans streptococci for sialic acid utilization as a sole carbon source.
- Analyzed metabolic end-products (formate, acetate, ethanol, lactate) from sialic acid and glucose metabolism.
- Assessed enzyme activities (N-acetylneuraminate pyruvate-lyase, N-acetylglucosamine-6-phosphate deacetylase, glucosamine-6-phosphate deaminase) in cell-free extracts from bacteria grown on sialic acid versus glucose.
Main Results:
- S. oralis, S. sanguis, S. gordonii, S. mitis, S. intermedius, S. anginosus, S. constellatus, and S. defectivus efficiently utilized sialic acid as a sole carbon source.
- Metabolism of sialic acid yielded formate, acetate, and ethanol, distinct from lactate produced during glucose metabolism.
- Sialic acid-grown cells showed elevated levels of key catabolic enzymes (NPL, GlcNAc-6-P deacetylase, GlcN-6-P deaminase), which were repressed by glucose.
Conclusions:
- The ability to utilize sialic acid is present in viridans streptococci species most frequently associated with extra-oral diseases.
- This metabolic trait likely plays a significant role in the persistence and survival of these bacteria in vivo.
- Sialic acid catabolism involves specific enzymes, with evidence suggesting a pathway linked to N-acetylglucosamine metabolism.