Structural identities of four glycosylated lipids in the oral bacterium Streptococcus mutans UA159 |
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Authors: | Larry Sallans José-Luis Giner David J Kiemle Jenny E Custer Edna S Kaneshiro |
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Institution: | 1. Department of Chemistry, University of Cincinnati, Cincinnati, OH, 45221, USA;2. Department of Chemistry, State University of New York, ESF, Syracuse, NY, 13210, USA;3. Department of Biological Sciences, University of Cincinnati, Cincinnati, OH, 45221, USA |
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Abstract: | The cariogenic bacterium Streptococcus mutans is an important dental pathogen that forms biofilms on tooth surfaces, which provide a protective niche for the bacterium where it secretes organic acids leading to the demineralization of tooth enamel. Lipids, especially glycolipids are likely to be key components of these biofilm matrices. The UA159 strain of S. mutans was among the earliest microorganisms to have its genome sequenced. While the lipids of other S. mutans strains have been identified and characterized, lipid analyses of UA159 have been limited to a few studies on its fatty acids. Here we report the structures of the four major glycolipids from stationary-phase S. mutans UA159 cells grown in standing cultures. These were shown to be monoglucosyldiacylglycerol (MGDAG), diglucosyldiacylglycerol (DGDAG), diglucosylmonoacylglycerol (DGMAG) and, glycerophosphoryldiglucosyldiacylglycerol (GPDGDAG). The structures were determined by high performance thin-layer chromatography, mass spectrometry and nuclear magnetic resonance spectroscopy. The glycolipids were identified by accurate, high resolution, and tandem mass spectrometry. The identities of the sugar units in the glycolipids were determined by a novel and highly efficient NMR method. All sugars were shown to have α-glycosidic linkages and DGMAG was shown to be acylated in the sn-1 position by NMR. This is the first observation of unsubstituted DGMAG in any organism and the first mass spectrometry data for GPDGDAG. |
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Keywords: | BHI brain&ndash heart infusion BHT butylated hydroxytoluene CID collision-induced dissociation CL cardiolipin diphosphatidylglycerol COSY correlation spectroscopy DAG diacylglycerol ddH2O double-distilled water DGDAG diglucosyldiacylglycerol DGMAG diglucosylmonoacylglycerol DMSO dimethylsulfoxide FT-ICR Fourier transform ion cyclotron resonance GPDGDAG glycerophosphoryldiglucosyldiacylglycerol HPTLC high performance thin-layer chromatography MS mass spectrometry MGDAG monoglucosyldiacylglycerol NMR nuclear magnetic resonance NOESY nuclear Overhauser effect spectroscopy PG phosphatidylglycerol ROESY rotating-frame nuclear Overhauser effect spectroscopy TLC thin-layer chromatography TOCSY total correlation spectroscopy |
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