Dissertation/Thesis Abstract

Phospholipids and Glycolipids of the Oral Bacterium Streptococcus mutans UA159
by Custer, Jenny Elise, M.S., University of Cincinnati, 2011, 112; 10857048
Abstract (Summary)

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.

Indexing (document details)
Advisor:
Commitee: Kaneshiro, Edna, Tepperman, Katherine, Villegas, Eric
School: University of Cincinnati
Department: Biological Sciences
School Location: United States -- Ohio
Source: MAI 57/06M(E), Masters Abstracts International
Source Type: DISSERTATION
Subjects: Biology, Cellular biology
Keywords: Fatty acid profile, Glycolipids, Phospholipids, Streptococcus mutans
Publication Number: 10857048
ISBN: 9780438022409
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