Conservation of the glycogen metabolism pathway underlines a pivotal function of storage polysaccharides in Chlamydiae.

The order Chlamydiales includes obligate intracellular pathogens capable of infecting mammals, fishes and amoeba. Unlike other intracellular bacteria for which intracellular adaptation led to the loss of glycogen metabolism pathway, all chlamydial families maintained the nucleotide-sugar dependent glycogen metabolism pathway i.e. the GlgC-pathway with the notable exception of both Criblamydiaceae and Waddliaceae families. Through detailed genome analysis and biochemical investigations, we have shown that genome rearrangement events have resulted in a defective GlgC-pathway and more importantly we have evidenced a distinct trehalose-dependent GlgE-pathway in both Criblamydiaceae and Waddliaceae families. Altogether, this study strongly indicates that the glycogen metabolism is retained in all Chlamydiales without exception, highlighting the pivotal function of storage polysaccharides, which has been underestimated to date. We propose that glycogen degradation is a mandatory process for fueling essential metabolic pathways that ensure the survival and virulence of extracellular forms i.e. elementary bodies of Chlamydiales.

Complete Structure of the Enterococcal Polysaccharide Antigen (EPA) of Vancomycin-Resistant Enterococcus faecalis V583 Reveals that EPA Decorations Are Teichoic Acids Covalently Linked to a Rhamnopolysaccharide Backbone.

All enterococci produce a complex polysaccharide called the enterococcal polysaccharide antigen (EPA). This polymer is required for normal cell growth and division and for resistance to cephalosporins and plays a critical role in host-pathogen interaction. The EPA contributes to host colonization and is essential for virulence, conferring resistance to phagocytosis during the infection. Recent studies revealed that the "decorations" of the EPA polymer, encoded by genetic loci that are variable between isolates, underpin the biological activity of this surface polysaccharide. In this work, we investigated the structure of the EPA polymer produced by the high-risk enterococcal clonal complex Enterococcus faecalis V583. We analyzed purified EPA from the wild-type strain and a mutant lacking decorations and elucidated the structure of the EPA backbone and decorations. We showed that the rhamnan backbone of EPA is composed of a hexasaccharide repeat unit of C2- and C3-linked rhamnan chains, partially substituted in the C3 position by α-glucose (α-Glc) and in the C2 position by ß-N-acetylglucosamine (ß-GlcNAc). The so-called "EPA decorations" consist of phosphopolysaccharide chains corresponding to teichoic acids covalently bound to the rhamnan backbone. The elucidation of the complete EPA structure allowed us to propose a biosynthetic pathway, a first essential step toward the design of antimicrobials targeting the synthesis of this virulence factor.IMPORTANCE Enterococci are opportunistic pathogens responsible for hospital- and community-acquired infections. All enterococci produce a surface polysaccharide called EPA (enterococcal polysaccharide antigen) required for biofilm formation, antibiotic resistance, and pathogenesis. Despite the critical role of EPA in cell growth and division and as a major virulence factor, no information is available on its structure. Here, we report the complete structure of the EPA polymer produced by the model strain E. faecalis V583. We describe the structure of the EPA backbone, made of a rhamnan hexasaccharide substituted by Glc and GlcNAc residues, and show that teichoic acids are covalently bound to this rhamnan chain, forming the so-called "EPA decorations" essential for host colonization and pathogenesis. This report represents a key step in efforts to identify the structural properties of EPA that are essential for its biological activity and to identify novel targets to develop preventive and therapeutic approaches against enterococci.

Characterization of the 6-O-acetylated lipoglucuronomannogalactan a novel Cryptococcus neoformans cell wall polysaccharide.

Glucuronoxylomannogalactans (GXMGals) are characteristic capsular polysaccharides produced by the opportunistic fungus C. neoformans, which are implicated in cryptococcal virulence, via impairment of the host immune response. We determined for the first time the structure of a lipoglucuronomannogalactan (LGMGal), isolated from the surface of a mutant C. neoformans carrying a deletion in the UDP-GlcA decarboxylase gene. Monosaccharide composition and methylation analyses, as well as nuclear magnetic resonance spectroscopy were employed in discerning the structure. Our results show that the polysaccharide structure of the LGMGal differs from GXMGal by the absence of xylose and 2-O-acetylated mannose residues. LGMGal consists of a galactan main chain -[-6-α-Gal-]-, where every second Gal residue is substituted at O-3 with an oligosaccharide α-Man6OAc-3-α-Man-4-(ß-GlcA-3)-ß-Gal-; components in italic being non-stoichiometric. The substitution rate of ß-Galp units by GlcpA is 35%. Additionally, we determined that the glycolipid anchor of the LGMGal is based on an myo-inositol phosphoceramide composed of C18-phytosphingosine and monohydroxylated lignoceric acid (2OHC24:0 fatty acid).

Structure and biological activities of a hexosamine-rich cell wall polysaccharide isolated from the probiotic Lactobacillus farciminis.

Lactobacillus farciminis CIP 103136 is a bacterial strain with recognized probiotic properties. However, the mechanisms underlying such properties have only been partially elucidated. In this study, we isolated and purified a cell-wall associated polysaccharide (CWPS), and evaluated its biological role in vitro. The structure of CWPS and responses from stimulation of (i) human macrophage-like THP-1 cells, (ii) human embryonal kidney (HEK293) cells stably transfected with Toll-like receptors (TLR2 or TLR4) and (iii) human colonocyte-like T84 intestinal epithelial cells, upon exposure to CWPS were studied. The structure of the purified CWPS from L. farciminis CIP 103136 was analyzed by nuclear magnetic resonance (NMR), MALDI-TOF-TOF MS, and methylation analyses in its native form and following Smith degradation. It was shown to be a novel branched polysaccharide, composed of linear backbone of trisaccharide repeating units of: [→6αGlcpNAc1 → 4ßManpNAc1 → 4ßGlcpNAc1→] highly substituted with single residues of αGlcp, αGalp and αGlcpNAc. Subsequently, the lack of pro- or anti-inflammatory properties of CWPS was established on macrophage-like THP-1 cells. In addition, CWPS failed to modulate cell signaling pathways dependent of TLR2 and TLR4 in transfected HEK-cells. Finally, in T84 cells, CWPS neither influenced intestinal barrier integrity under basal conditions nor prevented TNF-α/IFN-γ cytokine-mediated epithelium impairment.

Sites for Dynamic Protein-Carbohydrate Interactions of O- and C-Linked Mannosides on the E. coli FimH Adhesin.

Antagonists of the Escherichia coli type-1 fimbrial adhesin FimH are recognized as attractive alternatives for antibiotic therapies and prophylaxes against acute and recurrent bacterial infections. In this study α-d-mannopyranosides O- or C-linked with an alkyl, alkene, alkyne, thioalkyl, amide, or sulfonamide were investigated to fit a hydrophobic substituent with up to two aryl groups within the tyrosine gate emerging from the mannose-binding pocket of FimH. The results were summarized into a set of structure-activity relationships to be used in FimH-targeted inhibitor design: alkene linkers gave an improved affinity and inhibitory potential, because of their relative flexibility combined with a favourable interaction with isoleucine-52 located in the middle of the tyrosine gate. Of particular interest is a C-linked mannoside, alkene-linked to an ortho-substituted biphenyl that has an affinity similar to its O-mannosidic analog but superior to its para-substituted analog. Docking of its high-resolution NMR solution structure to the FimH adhesin indicated that its ultimate, ortho-placed phenyl ring is able to interact with isoleucine-13, located in the clamp loop that undergoes conformational changes under shear force exerted on the bacteria. Molecular dynamics simulations confirmed that a subpopulation of the C-mannoside conformers is able to interact in this secondary binding site of FimH.

Distribution of the O-acetyl groups and ß-galactofuranose units in galactoxylomannans of the opportunistic fungus Cryptococcus neoformans.

Galactoxylomannans (GalXMs) are a mixture of neutral and acidic capsular polysaccharides produced by the opportunistic fungus Cryptococcus neoformans that exhibit potent suppressive effects on the host immune system. Previous studies describing the chemical structure of C. neoformans GalXMs have reported species without O-acetyl substituents. Herein we describe that C. neoformans grown in capsule-inducing medium produces highly O-acetylated GalXMs. The location of the O-acetyl groups was determined by nuclear magnetic resonance (NMR) spectroscopy. In the neutral GalXM (NGalXM), 80% of 3-linked mannose (α-Manp) residues present in side chains are acetylated at the O-2 position. In the acidic GalXM also termed glucuronoxylomannogalactan (GXMGal), 85% of the 3-linked α-Manp residues are acetylated either in the O-2 (75%) or in the O-6 (25%) position, but O-acetyl groups are not present at both positions simultaneously. In addition, NMR spectroscopy and methylation analysis showed that ß-galactofuranose (ß-Galf) units are linked to O-2 and O-3 positions of nonbranched α-galactopyranose (α-Galp) units present in the GalXMs backbone chain. These findings highlight new structural features of C. neoformans GalXMs. Among these features, the high degree of O-acetylation is of particular interest, since O-acetyl group-containing polysaccharides are known to possess a range of immunobiological activities.

Expanding the knowledge of the chemical structure of glycoconjugates from Trypanosoma cruzi TcI genotype. Contribution to taxonomic studies.

One of the main obstacles to the treatment of Chagas disease is the genetic and phenotypical variance displayed by T. cruzi strains, resulting in differences in morphology, virulence, pathogenicity and drug susceptibility. To better understand the role of glycoconjungates in Chagas disease, we performed the molecular characterization of the O-linked chains from mucins and glycoinositolphospholipids (GIPLs) of the Silvio X10 clone 1 strain. We demonstrated the presence of a ß-galactofuranose (ß-Galf) unity linked to the O-4 position of the α-N-acetylglucosamine (α-GlcNAc)O-4 in Tc-mucins. GIPLs analysis showed that the lipidic portion is exclusively composed of ceramide and the PI-oligossacharidic portion contains the Man4(AEP)GlcN-Ins-PO4 core, substituted by ethanolamine-phosphate (EtNP) on the third distal mannose from inositol, which may or may not have a terminal ß Galf unity. These results confirm the classification of the Silvio X10/1 strain in group T. cruzi I. Again, it is noted that the study of T. cruzi surface glycoconjugates confirm the molecular results and the hypothesis that surface glycoconjugates may be interesting biomarker for the differentiation of trypanosomatid strains.

Muc5ac gastric mucin glycosylation is shaped by FUT2 activity and functionally impacts Helicobacter pylori binding.

The gastrointestinal tract is lined by a thick and complex layer of mucus that protects the mucosal epithelium from biochemical and mechanical aggressions. This mucus barrier confers protection against pathogens but also serves as a binding site that supports a sheltered niche of microbial adherence. The carcinogenic bacteria Helicobacter pylori colonize the stomach through binding to host glycans present in the glycocalyx of epithelial cells and extracellular mucus. The secreted MUC5AC mucin is the main component of the gastric mucus layer, and BabA-mediated binding of H. pylori to MUC5AC confers increased risk for overt disease. In this study we unraveled the O-glycosylation profile of Muc5ac from glycoengineered mice models lacking the FUT2 enzyme and therefore mimicking a non-secretor human phenotype. Our results demonstrated that the FUT2 determines the O-glycosylation pattern of Muc5ac, with Fut2 knock-out leading to a marked decrease in α1,2-fucosylated structures and increased expression of the terminal type 1 glycan structure Lewis-a. Importantly, for the first time, we structurally validated the expression of Lewis-a in murine gastric mucosa. Finally, we demonstrated that loss of mucin FUT2-mediated fucosylation impairs gastric mucosal binding of H. pylori BabA adhesin, which is a recognized feature of pathogenicity.

Glycosylation of BclA Glycoprotein from Bacillus cereus and Bacillus anthracis Exosporium Is Domain-specific.

The spores of the Bacillus cereus group (B. cereus, Bacillus anthracis, and Bacillus thuringiensis) are surrounded by a paracrystalline flexible yet resistant layer called exosporium that plays a major role in spore adhesion and virulence. The major constituent of its hairlike surface, the trimerized glycoprotein BclA, is attached to the basal layer through an N-terminal domain. It is then followed by a repetitive collagen-like neck bearing a globular head (C-terminal domain) that promotes glycoprotein trimerization. The collagen-like region of B. anthracis is known to be densely substituted by unusual O-glycans that may be used for developing species-specific diagnostics of B. anthracis spores and thus targeted therapeutic interventions. In the present study, we have explored the species and domain specificity of BclA glycosylation within the B. cereus group. First, we have established that the collagen-like regions of both B. anthracis and B. cereus are similarly substituted by short O-glycans that bear the species-specific deoxyhexose residues anthrose and the newly observed cereose, respectively. Second we have discovered that the C-terminal globular domains of BclA from both species are substituted by polysaccharide-like O-linked glycans whose structures are also species-specific. The presence of large carbohydrate polymers covering the surface of Bacillus spores may have a profound impact on the way that spores regulate their interactions with biotic and abiotic surfaces and represents potential new diagnostic targets.

Candida albicans ß-1,2 mannosyl transferase Bmt3: Preparation and evaluation of a ß (1,2), α (1,2)-tetramannosyl fluorescent substrate.

We describe for the first time the chemical synthesis of a tetramannoside, containing both α (1→2) and ß (1→2) linkages. Dodecylthio (lauryl) glycosides were prepared from odorless dodecyl thiol and used as donors for the glycosylation steps. This tetramannoside, was coupled to a mantyl group, and revealed to be a perfect substrate of ß-mannosyltransferase Bmt3, confirming the proposed specificity and allowing the preparation of a pentamannoside sequence (ß Man (1,2) ß Man (1,2) α Man (1,2) α Man (1,2) α Man) usable as a novel substrate for further elongation studies.

Teichoic acid is the major polysaccharide present in the Listeria monocytogenes biofilm matrix.

The aim of this study was to characterize the Listeria monocytogenes biofilm and particularly the nature of the carbohydrates in the biofilm extracellular matrix and culture supernatant versus to cell wall carbohydrates. Listeria monocytogenes serotype 1/2a and 4b strains were able to form complex biofilms embedded in an extracellular matrix. The soluble carbohydrates from biofilm extracellular matrix and culture supernatant were identified as teichoic acids, structurally identical to cell wall teichoic acids. In addition, the DSS 1130 BFA2 strain had a serotype 1/2a teichoic acid lacking N-acetyl glucosamine glycosylation due to a mutation in the lmo2550 gene. Consequently, we hypothesized that the extracellular teichoic acids in L. monocytogenes biofilms have the same origin as cell wall teichoic acid.

Revisiting Plant Plasma Membrane Lipids in Tobacco: A Focus on Sphingolipids.

The lipid composition of plasma membrane (PM) and the corresponding detergent-insoluble membrane (DIM) fraction were analyzed with a specific focus on highly polar sphingolipids, so-called glycosyl inositol phosphorylceramides (GIPCs). Using tobacco (Nicotiana tabacum) 'Bright Yellow 2' cell suspension and leaves, evidence is provided that GIPCs represent up to 40 mol % of the PM lipids. Comparative analysis of DIMs with the PM showed an enrichment of 2-hydroxylated very-long-chain fatty acid-containing GIPCs and polyglycosylated GIPCs in the DIMs. Purified antibodies raised against these GIPCs were further used for immunogold-electron microscopy strategy, revealing the distribution of polyglycosylated GIPCs in domains of 35 ± 7 nm in the plane of the PM. Biophysical studies also showed strong interactions between GIPCs and sterols and suggested a role for very-long-chain fatty acids in the interdigitation between the two PM-composing monolayers. The ins and outs of lipid asymmetry, raft formation, and interdigitation in plant membrane biology are finally discussed.

Candida albicans ß-1,2-mannosyltransferase Bmt3 prompts the elongation of the cell-wall phosphopeptidomannan.

ß-1,2-Linked mannosides are expressed on numerous cell-wall glycoconjugates of the opportunistic pathogen yeast Candida albicans. Several studies evidenced their implication in the host-pathogen interaction and virulence mechanisms. In the present study, we characterized the in vitro activity of CaBmt3, a ß-1,2-mannosyltransferase involved in the elongation of ß-1,2-oligomannosides oligomers onto the cell-wall polymannosylated N-glycans. A recombinant soluble enzyme Bmt3p was produced in Pichia pastoris and its enzyme activity was investigated using natural and synthetic oligomannosides as potential acceptor substrates. Bmt3p was shown to exhibit an exquisite enzymatic specificity by adding a single terminal ß-mannosyl residue to α-1,2-linked oligomannosides capped by a Manß1-2Man motif. Furthermore, we demonstrated that the previously identified CaBmt1 and CaBmt3 efficiently act together to generate Manß1-2Manß1-2[Manα1-2]n sequence from α-1,2-linked oligomannosides onto exogenous and endogenous substrates.

ß-1,2-Mannosyltransferases 1 and 3 Participate in Yeast and Hyphae O- and N-Linked Mannosylation and Alter Candida albicans Fitness During Infection.

ß-1,2-mannosylation of Candida albicans glycoconjugates has been investigated through the identification of enzymes involved in the addition of ß-1,2-oligomannosides (ß-Mans) to phosphopeptidomannan and phospholipomannan. ß-1,2-oligomannosides are supposed to have virulence properties that they confer to these glycoconjugates. In a previous study, we showed that cell wall mannoproteins (CWMPs) harbor ß-Mans in their O-mannosides; therefore, we analyzed their biosynthesis and impact on virulence. In this study, we demonstrate that O-mannans are heterogeneous and that α-mannosylated O-mannosides, which are biosynthesized by Mnt1 and Mnt2 α-1,2-mannosyltransferases, can be modified with ß-Mans but only at the nonreducing end of α-1,2-mannotriose. ß-1,2-mannosylation of this O-mannotriose depends on growth conditions, and it involves 2 ß-1,2-mannosyltransferases, Bmt1 and Bmt3. These Bmts are essential for ß-1,2-mannosylation of CWMPs and expression of ß-Mans on germ tubes. A bmt1Δ mutant and a mutant expressing no ß-Mans unexpectedly disseminated more in BALB/c mice, whereas they had neither attenuated nor enhanced virulence in C57BL/6 mice. In galectin (Gal)3 knockout mice, the reference strain was more virulent than in C57BL/6 mice, suggesting that the ß-Mans innate receptor Gal3 is involved in C. albicans fitness during infection.

Presence and function of a thick mucous layer rich in polysaccharides around Bacillus subtilis spores.

This study was designed to establish the presence and function of the mucous layer surrounding spores of Bacillus subtilis. First, an external layer of variable thickness and regularity was often observed on B. subtilis spores. Further analyses were performed on B. subtilis 98/7 spores surrounded by a thick layer. The mechanical removal of the layer did not affect their resistance to heat or their ability to germinate but rendered the spore less hydrophilic, more adherent to stainless steel, and more resistant to cleaning. This layer was mainly composed of 6-deoxyhexoses, ie rhamnose, 3-O-methyl-rhamnose and quinovose, but also of glucosamine and muramic lactam, known also to be a part of the bacterial peptidoglycan. The specific hydrolysis of the peptidoglycan using lysozyme altered the structure of the required mucous layer and affected the physico-chemical properties of the spores. Such an outermost mucous layer has also been seen on spores of B. licheniformis and B. clausii isolated from food environments.

The lacdiNAc-specific adhesin LabA mediates adhesion of Helicobacter pylori to human gastric mucosa.

Adhesion of Helicobacter pylori to the gastric mucosa is a necessary prerequisite for the pathogenesis of H. pylori-related diseases. In this study, we investigated the GalNAcß1-4GlcNAc motif (also known as N,N'-diacetyllactosediamine [lacdiNAc]) carried by MUC5AC gastric mucins as the target for bacterial binding to the human gastric mucosa. The expression of LacdiNAc carried by gastric mucins was correlated with H. pylori localization, and all strains tested adhered significantly to this motif. Proteomic analysis and mutant construction allowed the identification of a yet uncharacterized bacterial adhesin, LabA, which specifically recognizes lacdiNAc. These findings unravel a target of adhesion for H. pylori in addition to moieties recognized by the well-characterized adhesins BabA and SabA. Localization of the LabA target, restricted to the gastric mucosa, suggests a plausible explanation for the tissue tropism of these bacteria. These results pave the way for the development of alternative strategies against H. pylori infection, using adherence inhibitors.

Characterization of the recombinant Candida albicans ß-1,2-mannosyltransferase that initiates the ß-mannosylation of cell wall phosphopeptidomannan.

The presence of ß-mannosides in their cell walls confers specific features on the pathogenic yeasts Candida albicans and Candida glabrata compared with non-pathogenic yeasts. In the present study, we investigated the enzymatic properties of Bmt1 (ß-mannosyltransferase 1), a member of the recently identified ß-mannosyltransferase family, from C. albicans. A recombinant soluble enzyme lacking the N-terminal region was expressed as a secreted protein from the methylotrophic yeast Pichia pastoris. In parallel, functionalized natural oligosaccharides isolated from Saccharomyces cerevisiae and a C. albicans mutant strain, as well as synthetic α-oligomannosides, were prepared and used as potential acceptor substrates. Bmt1p preferentially utilizes substrates containing linear chains of α-1,2-linked mannotriose or mannotetraose. The recombinant enzyme consecuti-vely transfers two mannosyl units on to these acceptors, leading to the production of α-mannosidase-resistant oligomannosides. NMR experiments further confirmed the presence of a terminal ßMan (ß-1,2-linked mannose) unit in the first enzyme product. In the future, a better understanding of specific ß-1,2-mannosyltransferase molecular requirements will help the design of new potential antifungal drugs.

Convergent evolution of polysaccharide debranching defines a common mechanism for starch accumulation in cyanobacteria and plants.

Starch, unlike hydrosoluble glycogen particles, aggregates into insoluble, semicrystalline granules. In photosynthetic eukaryotes, the transition to starch accumulation occurred after plastid endosymbiosis from a preexisting cytosolic host glycogen metabolism network. This involved the recruitment of a debranching enzyme of chlamydial pathogen origin. The latter is thought to be responsible for removing misplaced branches that would otherwise yield a water-soluble polysaccharide. We now report the implication of starch debranching enzyme in the aggregation of semicrystalline granules of single-cell cyanobacteria that accumulate both glycogen and starch-like polymers. We show that an enzyme of analogous nature to the plant debranching enzyme but of a different bacterial origin was recruited for the same purpose in these organisms. Remarkably, both the plant and cyanobacterial enzymes have evolved through convergent evolution, showing novel yet identical substrate specificities from a preexisting enzyme that originally displayed the much narrower substrate preferences required for glycogen catabolism.

Structural studies of the cell wall polysaccharides from three strains of Lactobacillus helveticus with different autolytic properties: DPC4571, BROI, and LH1.

Lactobacillus helveticus is traditionally used in dairy industry as a starter or an adjunct culture for manufacture of cheese and some types of fermented milk. Its autolysis releases intracellular enzymes which is a prerequisite for optimum cheese maturation, and is known to be strain dependent. Autolysis is caused by an enzymatic hydrolysis of the cell wall peptidoglycan (PG) by endogenous peptidoglycan hydrolases (PGHs) or autolysins. Origins of differences in autolytic properties of different strains are not fully elucidated. Regulation of autolysis possibly depends on the structure of the cell wall components other than PG, particularly polysaccharides. In the present work, we screened six L. helveticus strains with different autolytic properties: DPC4571, BROI and LH1. We established, for the first time, that cell walls (CWs) of these strains contained polysaccharides, different from their CW teichoic acids. Cell wall polysaccharides of three strains were purified, and their chemical structures were established by 2D NMR spectroscopy and methylation analysis. The structures of their repeating units are presented.

Modulation of intestinal inflammation by yeasts and cell wall extracts: strain dependence and unexpected anti-inflammatory role of glucan fractions.

Yeasts and their glycan components can have a beneficial or adverse effect on intestinal inflammation. Previous research has shown that the presence of Saccharomyces cerevisiae var. boulardii (Sb) reduces intestinal inflammation and colonization by Candida albicans. The aim of this study was to identify dietary yeasts, which have comparable effects to the anti-C. albicans and anti-inflammatory properties of Sb and to assess the capabilities of yeast cell wall components to modulate intestinal inflammation. Mice received a single oral challenge of C. albicans and were then given 1.5% dextran-sulphate-sodium (DSS) for 2 weeks followed by a 3-day restitution period. S. cerevisiae strains (Sb, Sc1 to Sc4), as well as mannoprotein (MP) and ß-glucan crude fractions prepared from Sc2 and highly purified ß-glucans prepared from C. albicans were used in this curative model, starting 3 days after C. albicans challenge. Mice were assessed for the clinical, histological and inflammatory responses related to DSS administration. Strain Sc1-1 gave the same level of protection against C. albicans as Sb when assessed by mortality, clinical scores, colonization levels, reduction of TNFα and increase in IL-10 transcription. When Sc1-1 was compared with the other S. cerevisiae strains, the preparation process had a strong influence on biological activity. Interestingly, some S. cerevisiae strains dramatically increased mortality and clinical scores. Strain Sc4 and MP fraction favoured C. albicans colonization and inflammation, whereas ß-glucan fraction was protective against both. Surprisingly, purified ß-glucans from C. albicans had the same protective effect. Thus, some yeasts appear to be strong modulators of intestinal inflammation. These effects are dependent on the strain, species, preparation process and cell wall fraction. It was striking that ß-glucan fractions or pure ß-glucans from C. albicans displayed the most potent anti-inflammatory effect in the DSS model.