Unique cholesteryl glucosides in Helicobacter pylori: composition and structural analysis

Abstract

A chloroform-methanol-extracted lipid of Helicobacter pylori was studied. Three kinds of glycolipids, accounting for about 25% (wt/wt) of the total lipid, were detected and identified to be cholesteryl glucosides. The structures of two of them were determined to be cholesteryl-␣-D-glucopyranoside and cholesteryl-6-O-tetradecanoyl-␣-D-glucopyranoside, and the plausible structure of the third one was identified as cholesteryl-6-Ophosphatidyl-␣-D-glucopyranoside. Cholesteryl glucosides are very rare in animals and bacteria. Furthermore, those in H. pylori had an ␣-glycosidic linkage, which is rather unusual for natural glycosides, and a phosphatelinked cholesteryl glycoside like the cholesteryl-6-O-phosphatidyl-␣-D-glucopyranoside has not been reported previously. As the cholesterol glucosides were detected in strains obtained from diverse geographical locations, the presence of cholesteryl glucosides in H. pylori is a very unique and a characteristic feature of the species. These findings add a new facet to the physiology and biochemistry, especially the cholesterol and glucose metabolism, of H. pylori. Furthermore, the cholesteryl glucosides of H. pylori showed hemolytic activities.Helicobacter pylori is a curved gram-negative bacterium which was first reported in 1983 (21, 35). The organism is now recognized as a primary cause of active chronic gastritis and is reported to be associated with peptic ulcer disease, gastric adenocarcinoma, and low-grade B-cell gastric lymphoma of mucosa-associated lymphoid tissue (4,14,36).The organism can colonize in and under the mucus layer of the human gastric mucosa without the copresence of other bacterial species. It, living in the unique gastric environment, is likely to have features distinct from other bacteria. Furthermore, it has been found to possess a unique urease having a very low K m value, which hydrolyzes urea efficiently even at the low urea concentration found in the gastric mucosa (13,24).On the other hand, the lipid composition of microorganisms can adapt in response to alterations of environmental conditions (15, 25), and those living in unique environments may have special lipids (5). It is likely that H. pylori living in the gastric niche may have a distinct lipid composition or structure. The fatty acid composition of H. pylori has been studied extensively (9, 10, 19), and it has been shown that the cellular fatty acids 3-OH C 16:0 and 3-OH C 18:0 are unique to this organism. However, little is known about the polar lipid composition of H. pylori.Therefore, we studied the lipid composition of H. pylori and detected three kinds of glycolipids, which were identified as cholesteryl glucosides (CGs). Additionally, the molecular structures of these CGs have been determined. MATERIALS AND METHODSBacterial strains and growth conditions. H. pylori NCTC 11638 was mainly used in this study. H. pylori ATCC 43504 and two clinical isolates of H. pylori obtained from Japan and Bangladesh were used for comparison. These were grown in brain heart infusion broth (Difco, D...

A newly discovered cholesteryl galactoside from Borrelia burgdorferi

“…Cholesteryl glycosides have been identified in Mycoplasmas (20,23), H. pylori (21), and Borrelia hermsi (24), in all of which, the carbohydrate was glucose. Cholesteryl Galactoside is now identified in bacteria.…”

“…Free cholesterol or cholesterol esters are components of several bacterial membranes such as Mycoplasma (20), Helicobacter pylori (21), Micrococcus lysodeikticus, Bacillus megaterium, and Proteus mirabilis (22). Cholesteryl glycosides have been identified in Mycoplasmas (20,23), H. pylori (21), and Borrelia hermsi (24), in all of which, the carbohydrate was glucose.…”

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