Mucins in the mucosal barrier to infection.

Aims: To investigate the antimicrobial properties of phenolic compounds present in Finnish berries against probiotic bacteria and other intestinal bacteria, including pathogenic species.

Methods and Results: Antimicrobial activity of pure phenolic compounds representing flavonoids and phenolic acids, and eight extracts from common Finnish berries, was measured against selected Gram-positive and Gram-negative bacterial species, including probiotic bacteria and the intestinal pathogen Salmonella. Antimicrobial activity was screened by an agar diffusion method and bacterial growth was measured in liquid culture as a more accurate assay. Myricetin inhibited the growth of all lactic acid bacteria derived from the human gastrointestinal tract flora but it did not affect the Salmonella strain. In general, berry extracts inhibited the growth of Gram-negative but not Gram-positive bacteria. These variations may reflect differences in cell surface structures between Gram-negative and Gram-positive bacteria. Cloudberry, raspberry and strawberry extracts were strong inhibitors of Salmonella. Sea buckthorn berry and blackcurrant showed the least activity against Gram-negative bacteria.

Conclusions: Different bacterial species exhibit different sensitivities towards phenolics.

Significance and Impact of the Study: These properties can be utilized in functional food development and in food preservative purposes.

https://onlinelibrary.wiley.com/doi/pdf/10.1046/j.1365-2672.2001.01271.x

Antimicrobial properties of phenolic compounds from berries

Improvement in shelf-life and safety of perishable foods by plant essential oils and smoke antimicrobials

Sialic acids are one of the most important molecules of life, since they occupy the terminal position on macromolecules and cell membranes and are involved in many biological and pathological phenomena. The structures of sialic acids, comprising a family of over 40 neuraminic acid derivatives, have been elucidated. However, many aspects of the regulation of their metabolism at the enzyme and gene levels, as well as of their functions remain mysterious. Sialic acids play a dual role, not only are they indispensable for the protection to and adaptation of life, but are also utilised by life-threatening infectious microorganisms. In this article the present state of knowledge in sialobiology, with an emphasis on my personal experience in this research area, is outlined including a discussion of necessary future work in this fascinating field of cell biology.

/pdf/achievements-and-challenges-of-sialic-acid-research-4ya9a4cpft.pdf

Achievements and challenges of sialic acid research.

Eukaryotic organisms as well as some prokaryotes and viruses contain sphingolipids, which are defined by a common structural feature, i.e. , a "sphingoid base" backbone such as D-erythro-1,3-dihydroxy, 2-aminooctadec-4-ene (sphingosine). The sphingolipids of mammalian tissues, lipoproteins, and milk include ceramides, sphingomyelins, cerebrosides, gangliosides and sulfatides; plants, fungi and yeast have mainly cerebrosides and phosphoinositides. The total amounts of sphingolipids in food vary considerably, from a few micromoles per kilogram (fruits) to several millimoles per kilogram in rich sources such as dairy products, eggs and soybeans. With the use of the limited data available, per capita sphingolipid consumption in the United States can be estimated to be on the order of 150-180 mmol (approximately 115-140 g) per year, or 0.3-0.4 g/d. There is no known nutritional requirement for sphingolipids; nonetheless, they are hydrolyzed throughout the gastrointestinal tract to the same categories of metabolites (ceramides and sphingoid bases) that are used by cells to regulate growth, differentiation, apoptosis and other cellular functions. Studies with experimental animals have shown that feeding sphingolipids inhibits colon carcinogenesis, reduces serum LDL cholesterol and elevates HDL, suggesting that sphingolipids represent a "functional" constituent of food. Sphingolipid metabolism can also be modified by constituents of the diet, such as cholesterol, fatty acids and mycotoxins (fumonisins), with consequences for cell regulation and disease. Additional associations among diet, sphingolipids and health are certain to emerge as more is learned about these compounds.

/pdf/sphingolipids-in-food-and-the-emerging-importance-of-21zopq8qbz.pdf

Sphingolipids in Food and the Emerging Importance of Sphingolipids to Nutrition

Effects of aqueous extracts of medicinal plants on ten Helicobacter pylori strains were studied by the salt aggregation test to determine the possibility to modulate their cell surface hydrophobicity and by an agar diffusion assay for detection of antimicrobial activity. It was established that aqueous extracts of bearberry and cowberry leaves enhance cell aggregation of all H. pylori strains tested by the salt aggregation test, and the extract of bearberry possessed a remarkable bacteriostatic activity. Pure tannic acid showed a result similar to that of bearberry and cowberry extracts which contained a large amount of tannins. In contrast, extracts of wild camomile and pineapple-weed, which blocked aggregation of H. pylori, contained small amounts of tannins and did not reveal any antimicrobial activity. Tannic acid seems to be the component of bearberry and cowberry aqueous extracts with the highest activity to decrease cell surface hydrophobicity as well as in antibacterial activity against H. pylori.

Effect on cell surface hydrophobicity and susceptibility of Helicobacter pylori to medicinal plant extracts.

Helicobacter pylori is a human pathogen associated with gastritis and peptic ulcer. Adhesion properties ofH. pylori to various structures have been described in the literature, including evidence for sialic acid-binding. To study the specificity and frequency of sialic acid-binding, fourteenH. pylori strains were investigated using haemagglutination with derivatized erythrocytes carrying sialic acids only on defined glycans and using haemagglutination inhibition assays. From these studiesH. pylori strains can be grouped into sialic acid-dependent and sialic acid-independent classes. The sialic acid-dependent strains require α-2,3-linked sialic acid for haemagglutination. The potential roles of sialic acid-dependent adhesions forH. pylori-related infections are discussed.

Adhesion of Helicobacter pylori strains to alpha-2,3-linked sialic acids.

Helicobacter pylori, a human gastric pathogen causing chronic gastritis and duodenal ulcer disease, has been found in large amounts in gastric mucous gel layer Mucin preparations, separated from human gastric juices and isolated from different colon regions, were examined for their ability to inhibit haemagglutination of H pylori with the emphasis on evaluating the role of sialic acid-dependent haemagglutinins of the bacteria in colonisation of the stomach The mucins showed high inhibitory activity for H pylori, which was significantly decreased after the removal of sialic acids from the mucins The inhibitory potencies using high molecular mass mucin-like components from bovine milk were comparable with those obtained for gastric mucins, suggesting their possible role in the prevention of H pylori infection

Inhibition of Helicobacter pylori sialic acid-specific haemagglutination by human gastrointestinal mucins and milk glycoproteins

Plant and animal lectins with various carbohydrate specificities were used to type 35 Irish clinical isolates of Helicobacter pylori and the type strain NCTC 11637 in a microtiter plate assay. Initially, a panel of eight lectins with the indicated primary specificities were used: Anguilla anguilla (AAA), Lotus tetragonolobus (Lotus A), and Ulex europaeus I (UEA I), specific for -L-fucose; Solanum tuberosum (STA) and Triticum vulgaris (WGA), specific for -N-acetylglucosamine; Glycine max (SBA), specific for -N-acetylgalactosamine; Erythrina cristagali (ECA), specific for -galactose and -N-acetylgalactosamine; and Lens culinaris (LCA), specific for -mannose and -glucose. Three of the lectins (SBA, STA, and LCA) were not useful in aiding in strain discrimination. An optimized panel of five lectins (AAA, ECA, Lotus A, UEA I, and WGA) grouped all 36 strains tested into eight lectin reaction patterns. For optimal typing, pretreatment by washing bacteria with a low-pH buffer to allow protein release, followed by proteolytic degradation to eliminate autoagglutination, was used. Lectin types of treated samples were stable and reproducible. No strain proved to be untypeable by this system. Electrophoretic and immunoblotting analyses of lipopolysaccharides (LPSs) indicated that the lectins interact primarily, but not solely, with the O side chain of H. pylori LPS. (Less)

/pdf/differentiation-of-helicobacter-pylori-isolates-based-on-257va9ieoi.pdf

Differentiation of Helicobacter pylori isolates based on lectin binding of cell extracts in an agglutination assay.

Heparan sulphate binding to Helicobacter pylori at pH 4 to 5 was inhibited with various sulphated polysaccharides (heparin and chondroitin sulphates, fucoidan, carrageenans and some others), but not by carboxylated or nonsulphated compounds. Heparin binding proteins are exposed on the cell surface.

Siiri Hirmo

Papers

Effect on cell surface hydrophobicity and susceptibility of Helicobacter pylori to medicinal plant extracts.

Adhesion of Helicobacter pylori strains to alpha-2,3-linked sialic acids.

Inhibition of Helicobacter pylori sialic acid-specific haemagglutination by human gastrointestinal mucins and milk glycoproteins

Differentiation of Helicobacter pylori isolates based on lectin binding of cell extracts in an agglutination assay.

Inhibition of heparan sulphate and other glycosaminoglycans binding to Helicobacter pylori by various polysulphated carbohydrates.