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Structural studies of the serotype-f polysaccharide antigen from Streptococcus mutans OMZ175
R Linzer1, M S Reddy, M J Levine
1Department of Endodontics, State University of New York at Buffalo 14214.
Abstract:
The serotype f antigen of Streptococcus mutans has been described as a rhamnose-glucose polysaccharide associated with the bacterial cell wall. In this study, the structure of serotype f polysaccharide was examined by analyses of the methylated derivatives of the antigen and the periodate-oxidized antigen. Methylated derivatives were characterized with a gas chromatograph-mass spectrometer. The polysaccharide appeared to have a backbone of alternating 1,3- and 1,2,3-linked rhamnose units. Branching occurred at the 3-position of the 1,2,3-linked rhamnose. Side chains were composed of terminal alpha-linked glucose units. A small proportion of longer side chains containing 1,2- and 1,6-linked glucose units were noted in some preparations; however, these determinants were not reactive with serotype f antisera.
Insights
The Streptococcus mutans serotype f antigen is a rhamnose-glucose polysaccharide. This study reveals its detailed structure, identifying alternating rhamnose units and terminal alpha-linked glucose in the bacterial cell wall.
Area of Science:
- Microbiology
- Carbohydrate Chemistry
- Structural Biology
Background:
- Streptococcus mutans is a key bacterium in dental caries.
- The serotype f antigen is a cell wall component of S. mutans.
- Previous descriptions identified it as a rhamnose-glucose polysaccharide.
Purpose of the Study:
- To elucidate the detailed structure of the Streptococcus mutans serotype f polysaccharide.
- To characterize the linkage and branching patterns of the polysaccharide components.
Main Methods:
- Analysis of methylated derivatives of the serotype f antigen.
- Periodate oxidation of the antigen.
- Characterization of derivatives using gas chromatography-mass spectrometry (GC-MS).
Main Results:
- The polysaccharide backbone consists of alternating 1,3- and 1,2,3-linked rhamnose units.
- Branching occurs at the 3-position of the 1,2,3-linked rhamnose units.
- Side chains are primarily composed of terminal alpha-linked glucose units, with minor longer glucose chains not reactive with serotype f antisera.
Conclusions:
- The detailed structure of the Streptococcus mutans serotype f antigen has been determined.
- The identified structure provides insights into the molecular basis of serotype f specificity.
- Understanding this structure may aid in developing targeted interventions against S. mutans.