Streptococcus mutans is a gram-positive oral bacterium that forms biofilms and is the major etiological agent in the formation of dental caries. S. mutans metabolizes sugars and produces lactic acid, which accumulate in the biofilm and lead to a reduction in the environmental pH and demineralization of the tooth enamel. Although previous lipid analyses have been reported for S. mutans strains, in the present study, S. mutans strain UA159 was analyzed since the genome of the strain has been sequenced. Also, the total fatty acid composition of this and other S. mutans strains have been characterized, but there is a lack of information on the fatty acid composition of individual lipid classes and also on the full spectrum of lipids produced by this particular strain. Differences were observed in the lipid composition of organisms at different stages of culture growth. Five lipid classes were detected in log phase cells; however, more than nine lipid components were detected in stationary phase cells. Significant changes in the relative amounts of certain lipid classes present also occurred with the progression from log to stationary phase. The major lipid classes of S. mutans strain UA159 were identified by mass spectrometry (MS) and the definitive structures, including the nature of linkages for the glycosylated lipids were determined by nuclear magnetic resonance (NMR) spectroscopy.. The lipid classes that were identified included glucosyldiacylglycerol (GD), phosphatidylethanolamine (PE), phosphatidylserine (PS), diglucosyldiacylglycerol (DGD), lyso-diglucosylglyceride (lyso-DGG), phosphatidylglycerol (PG), cardiolipin (CL), and glycerophosphoryldiglucosyldiacylglycerol (PG-DGD). Saturated and monounsaturated fatty acids (14:0, 14:1, 16:0, 16:1, 18:0, 18:1, 20:0, 20:1) were identified by gas-liquid chromatography. The major fatty acids were 16:0, 18:1 and 20:1. With increased culture age and cell density there were significant increases in both the relative proportion of unsaturated to saturated fatty acids (&SigmaU/&SigmaS) and in the ratio of short chain (C14 + C16) to long-chain (C18 + C20) fatty acids (&SigmaS/&SigmaL). Analyses of individual lipid classes indicated that changes in the fatty acid composition of the individual lipid classes occurred during culture aging. With the exceptions of PE and PS all other classes detected in both log and stationary phases showed increases in the unsaturation index with increased culture age and an overall increase in chain length. These results indicate that changes seen in the fatty acid profile of the total polar lipid fraction reflects changes in both lipid class composition and changes to the fatty acid profile within individual lipid classes. The results also demonstrate that there is a significant increase in the relative amounts of unsaturated and long chain fatty acids in late stationary phase.
|Commitee:||Kaneshiro, Edna, Tepperman, Katherine, Villegas, Eric|
|School:||University of Cincinnati|
|School Location:||United States -- Ohio|
|Source:||MAI 57/06M(E), Masters Abstracts International|
|Subjects:||Biology, Cellular biology|
|Keywords:||Fatty acid profile, Glycolipids, Phospholipids, Streptococcus mutans|
Copyright in each Dissertation and Thesis is retained by the author. All Rights Reserved
The supplemental file or files you are about to download were provided to ProQuest by the author as part of a
dissertation or thesis. The supplemental files are provided "AS IS" without warranty. ProQuest is not responsible for the
content, format or impact on the supplemental file(s) on our system. in some cases, the file type may be unknown or
may be a .exe file. We recommend caution as you open such files.
Copyright of the original materials contained in the supplemental file is retained by the author and your access to the
supplemental files is subject to the ProQuest Terms and Conditions of use.
Depending on the size of the file(s) you are downloading, the system may take some time to download them. Please be