Analiza kwasow tluszczowych wystepujacych w lipopolisacharydach Bacteroides thetaiotaomicron i Bacteroides fragilis

Lipopolisacharydy (LPS) trzech szczepów B. thetaiotaomicron i czterech szczepów B. fragilis wyekstrahowano metodą fenolowo-wodną oraz oczyszczono za pomocą enzymów nukleolitycznych i ultrawirowania. Kwasy tłuszczowe lipopolisacharydów przeprowadzono w estry metylowe i analizowano metodą chromatografii gazowo-cieczowej sprzężonej ze spektrometrią masową (GLC-MS). Stwierdzono, że w LPS B. thetaiotaomicron i B. fragilis dominują długołańcuchowe kwasy tłuszczowe o 15-17 atomach węgla. Głównym kwasem tłuszczowym jest kwas 3-hydroksy-heksadekanowy (3OH C16:0). Zaobserwowano także występowanie kilku innych 3-hydroksy- kwasów tłuszczowych, co jest unikatową cechą lipopolisacharydów pałeczek z rodzaju Bacteroides.

The aim of this study was to determine and to compare fatty acids occurring in lipopolysacharides (LPS) isolated from B. thetaiotaomicron and B. fragilis strains of different origin. Lipopolysaccharides of three B. thetaiotaomicron strains and four B. fragilis strains were isolated by phenol-water extraction according to the procedure of Westphal and Jann (1965). Water-phase LPS fractions were then treated with nucleases and purified by ultracentrifugation as described by Gmeiner (1975). Fatty acid methyl esters, obtained by methanolysis of LPS, were analysed in gas-liquid chromatography combined with mass spectrometry (GLC-MS). Trimethylsilylated hydroxyl groups of fatty acid methyl esters were identified with GLC-MS using a method of selective ion monitoring (SIM). Lipopolysaccharides of B. thetaiotaomicron and B. fragilis strains contained long-chain (15-18 carbon atoms) fatty acids. The broad spectrum of simple long-chain and branched-chain fatty acids as well as 3-hydroxy fatty acids were detected. The main fatty acid of analyzed bacterial species was 3-hydroxy-hexadecanoic acid (30H C16:0). Several 3-hydroxy fatty acids were detected in LPS of examined strains. Fatty acids occurring in LPS of B. thetaiotaomicron and B. fragilis strains appeared to be qualitatively similar. Quantitative differences in fatty acids composition of lipopolysaccharides isolated from strains of different origin were observed.