The Mla system of diderm Firmicute Veillonella parvula reveals an ancestral transenvelope bridge for phospholipid trafficking.

E. coli and most other diderm bacteria (those with two membranes) have an inner membrane enriched in glycerophospholipids (GPLs) and an asymmetric outer membrane (OM) containing GPLs in its inner leaflet and primarily lipopolysaccharides in its outer leaflet. In E. coli, this lipid asymmetry is maintained by the Mla system which consists of six proteins: the OM lipoprotein MlaA extracts GPLs from the outer leaflet, and the periplasmic chaperone MlaC transfers them across the periplasm to the inner membrane complex MlaBDEF. However, GPL trafficking still remains poorly understood, and has only been studied in a handful of model species. Here, we investigate GPL trafficking in Veillonella parvula, a diderm Firmicute with an Mla system that lacks MlaA and MlaC, but contains an elongated MlaD. V. parvula mla mutants display phenotypes characteristic of disrupted lipid asymmetry which can be suppressed by mutations in tamB, supporting that these two systems have opposite GPL trafficking functions across diverse bacterial lineages. Structural modelling and subcellular localisation assays suggest that V. parvula MlaD forms a transenvelope bridge, comprising a typical inner membrane-localised MCE domain and, in addition, an outer membrane ß-barrel. Phylogenomic analyses indicate that this elongated MlaD type is widely distributed across diderm bacteria and likely forms part of the ancestral functional core of the Mla system, which would be composed of MlaEFD only.

Simultaneous Quantification of Trehalose and Trehalose 6-Phosphate by Hydrophilic Interaction Chromatography/Electrospray Accurate Mass Spectrometry with Application in Non-Targeted Metabolomics.

High-resolution mass spectrometry (HRMS) was coupled with ultra-high-performance liquid chromatography (UHPLC) to simultaneously quantify trehalose and trehalose 6-phosphate without derivatization or sample preparation. The use of full scan mode and exact mass analysis also makes it possible to carry out metabolomic analyses as well as semi-quantification. In addition, the use of different clusters in negative mode makes it possible to compensate for deficiencies in linearity and inerrant saturation at time-of-flight detectors. The method has been approved and validated for different matrices, yeasts, and bacteria, and has shown differentiation between bacteria as a function of growth temperatures.

A bioorthogonal chemistry approach to detect the K1 polysialic acid capsule in Escherichia coli.

Most Escherichia coli strains associated with neonatal meningitis express the K1 capsule, a sialic acid polysaccharide that is directly related to their pathogenicity. Metabolic oligosaccharide engineering (MOE) has mostly been developed in eukaryotes, but has also been successfully applied to the study of several oligosaccharides or polysaccharides constitutive of the bacterial cell wall. However, bacterial capsules are seldom targeted despite their important role as virulence factors, and the K1 polysialic acid (PSA) antigen that shields bacteria from the immune system still remains untackled. Herein, we report a fluorescence microplate assay that allows the fast and facile detection of K1 capsules with an approach that combines MOE and bioorthogonal chemistry. We exploit the incorporation of synthetic analogues of N-acetylmannosamine or N-acetylneuraminic acid, metabolic precursors of PSA, and copper-catalysed azide-alkyne cycloaddition (CuAAC) as the click chemistry reaction to specifically label the modified K1 antigen with a fluorophore. The method was optimized, validated by capsule purification and fluorescence microscopy, and applied to the detection of whole encapsulated bacteria in a miniaturized assay. We observe that analogues of ManNAc are readily incorporated into the capsule while those of Neu5Ac are less efficiently metabolized, which provides useful information regarding the capsule biosynthetic pathways and the promiscuity of the enzymes involved. Moreover, this microplate assay is transferable to screening approaches and may provide a platform to identify novel capsule-targeted antibiotics that would circumvent resistance issues.

Flagellar Phenotypes Impact on Bacterial Transport and Deposition Behavior in Porous Media: Case of Salmonella enterica Serovar Typhimurium.

Bacterial contamination of groundwater has always been an ecological problem worthy of attention. In this study, Salmonella enterica serovar Typhimurium with different flagellar phenotypes mainly characterized during host-pathogen interaction were analyzed for their transport and deposition behavior in porous media. Column transport experiments and a modified mobile-immobile model were applicated on different strains with flagellar motility (wild-type) or without motility (ΔmotAB), without flagella (ΔflgKL), methylated and unmethylated flagellin (ΔfliB), and different flagella phases (fliCON, fljBON). Results showed that flagella motility could promote bacterial transport and deposition due to their biological advantages of moving and attaching to surfaces. We also found that the presence of non-motile flagella improved bacterial adhesion according to a higher retention rate of the ΔmotAB strain compared to the ΔflgKL strain. This indicated that bacteria flagella and motility both had promoting effects on bacterial deposition in sandy porous media. Flagella phases influenced the bacterial movement; the fliCON strain went faster through the column than the fljBON strain. Moreover, flagella methylation was found to favor bacterial transport and deposition. Overall, flagellar modifications affect Salmonella enterica serovar Typhimurium transport and deposition behavior in different ways in environmental conditions.

Galleria mellonella as a Good Model to Study Acinetobacter baumannii Pathogenesis.

The invertebrate model, Galleria mellonella, has been widely used to study host-pathogen interactions due to its cheapness, ease of handling, and similar mammalian innate immune system. G. mellonella larvae have been proven to be useful and a reliable model for analyzing pathogenesis mechanisms of multidrug resistant Acinetobacter baumannii, an opportunistic pathogen difficult to kill. This review describes the detailed experimental design of G. mellonella/A. baumannii models, and provides a comprehensive comparison of various virulence factors and therapy strategies using the G. mellonella host. These investigations highlight the importance of this host-pathogen model for in vivo pathogen virulence studies. On the long term, further development of the G. mellonella/A. baumannii model will offer promising insights for clinical treatments of A. baumannii infection.

The role of l-arabinose metabolism for Escherichia coli O157:H7 in edible plants.

Arabinose is a major plant aldopentose in the form of arabinans complexed in cell wall polysaccharides or glycoproteins (AGP), but comparatively rare as a monosaccharide. l-arabinose is an important bacterial metabolite, accessed by pectolytic micro-organisms such as Pectobacterium atrosepticum via pectin and hemicellulose degrading enzymes. However, not all plant-associated microbes encode cell-wall-degrading enzymes, yet can metabolize l-arabinose, raising questions about their use of and access to the glycan in plants. Therefore, we examined l-arabinose metabolism in the food-borne pathogen Escherichia coli O157:H7 (isolate Sakai) during its colonization of plants. l-arabinose metabolism (araBA) and transport (araF) genes were activated at 18 °C in vitro by l-arabinose and expressed over prolonged periods in planta. Although deletion of araBAD did not impact the colonization ability of E. coli O157:H7 (Sakai) on spinach and lettuce plants (both associated with STEC outbreaks), araA was induced on exposure to spinach cell-wall polysaccharides. Furthermore, debranched and arabinan oligosaccharides induced ara metabolism gene expression in vitro, and stimulated modest proliferation, while immobilized pectin did not. Thus, E. coli O157:H7 (Sakai) can utilize pectin/AGP-derived l-arabinose as a metabolite. Furthermore, it differs fundamentally in ara gene organization, transport and regulation from the related pectinolytic species P. atrosepticum, reflective of distinct plant-associated lifestyles.

Colistin Treatment Affects Lipid Composition of Acinetobacter baumannii.

Multidrug-resistant Acinetobacter baumannii (A. baumannii) causes severe and often fatal healthcare-associated infections due partly to antibiotic resistance. There are no studies on A. baumannii lipidomics of susceptible and resistant strains grown at lethal and sublethal concentrations. Therefore, we analyzed the impact of colistin resistance on glycerolipids' content by using untargeted lipidomics on clinical isolate. Nine lipid sub-classes were annotated, including phosphatidylcholine, rarely detected in the bacterial membrane among 130 different lipid species. The other lipid sub-classes detected are phosphatidylethanolamine (PE), phosphatidylglycerol (PG), lysophosphatidylethanolamine, hemibismonoacylglycerophosphate, cardiolipin, monolysocardiolipin, diacylglycerol, and triacylglycerol. Under lethal and sublethal concentrations of colistin, significant reduction of PE was observed on the resistant and susceptible strain, respectively. Palmitic acid percentage was higher at colistin at low concentration but only for the susceptible strain. When looking at individual lipid species, the most abundant PE and PG species (PE 34:1 and PG 34:1) are significantly upregulated when the susceptible and the resistant strains are cultivated with colistin. This is, to date, the most exhaustive lipidomics data compilation of A. baumannii cultivated in the presence of colistin. This work is highlighting the plasma membrane plasticity used by this gram-negative bacterium to survive colistin treatment.

Escherichia coli O157:H7 F9 Fimbriae Recognize Plant Xyloglucan and Elicit a Response in Arabidopsis thaliana.

Fresh produce is often a source of enterohaemorrhagic Escherichia coli (EHEC) outbreaks. Fimbriae are extracellular structures involved in cell-to-cell attachment and surface colonisation. F9 (Fml) fimbriae have been shown to be expressed at temperatures lower than 37 °C, implying a function beyond the mammalian host. We demonstrate that F9 fimbriae recognize plant cell wall hemicellulose, specifically galactosylated side chains of xyloglucan, using glycan arrays. E. coli expressing F9 fimbriae had a positive advantage for adherence to spinach hemicellulose extract and tissues, which have galactosylated oligosaccharides as recognized by LM24 and LM25 antibodies. As fimbriae are multimeric structures with a molecular pattern, we investigated whether F9 fimbriae could induce a transcriptional response in model plant Arabidopsis thaliana, compared with flagella and another fimbrial type, E. coli common pilus (ECP), using DNA microarrays. F9 induced the differential expression of 435 genes, including genes involved in the plant defence response. The expression of F9 at environmentally relevant temperatures and its recognition of plant xyloglucan adds to the suite of adhesins EHEC has available to exploit the plant niche.

The Impact of Plasma Membrane Lipid Composition on Flagellum-Mediated Adhesion of Enterohemorrhagic Escherichia coli.

Enterohemorrhagic Escherichia coli (EHEC) O157:H7 is a major cause of foodborne gastrointestinal illness. The adhesion of EHEC to host tissues is the first step enabling bacterial colonization. Adhesins such as fimbriae and flagella mediate this process. Here, we studied the interaction of the bacterial flagellum with the host cell's plasma membrane using giant unilamellar vesicles (GUVs) as a biologically relevant model. Cultured cell lines contain many different molecular components, including proteins and glycoproteins. In contrast, with GUVs, we can characterize the bacterial mode of interaction solely with a defined lipid part of the cell membrane. Bacterial adhesion on GUVs was dependent on the presence of the flagellar filament and its motility. By testing different phospholipid head groups, the nature of the fatty acid chains, or the liposome curvature, we found that lipid packing is a key parameter to enable bacterial adhesion. Using HT-29 cells grown in the presence of polyunsaturated fatty acid (α-linolenic acid) or saturated fatty acid (palmitic acid), we found that α-linolenic acid reduced adhesion of wild-type EHEC but not of a nonflagellated mutant. Finally, our results reveal that the presence of flagella is advantageous for the bacteria to bind to lipid rafts. We speculate that polyunsaturated fatty acids prevent flagellar adhesion on membrane bilayers and play a clear role for optimal host colonization. Flagellum-mediated adhesion to plasma membranes has broad implications for host-pathogen interactions.IMPORTANCE Bacterial adhesion is a crucial step to allow bacteria to colonize their hosts, invade tissues, and form biofilm. Enterohemorrhagic Escherichia coli O157:H7 is a human pathogen and the causative agent of diarrhea and hemorrhagic colitis. Here, we use biomimetic membrane models and cell lines to decipher the impact of lipid content of the plasma membrane on enterohemorrhagic E. coli flagellum-mediated adhesion. Our findings provide evidence that polyunsaturated fatty acid (α-linolenic acid) inhibits E. coli flagellar adhesion to the plasma membrane in a mechanism separate from its antimicrobial and anti-inflammatory functions. In addition, we confirm that cholesterol-enriched lipid microdomains, often called lipid rafts, are important in bacterial adhesion. These findings demonstrate that plasma membrane adhesion via bacterial flagella play a significant role for an important human pathogen. This mechanism represents a promising target for the development of novel antiadhesion therapies.

The interaction of Escherichia coli O157 :H7 and Salmonella Typhimurium flagella with host cell membranes and cytoskeletal components.

Bacterial flagella have many established roles beyond swimming motility. Despite clear evidence of flagella-dependent adherence, the specificity of the ligands and mechanisms of binding are still debated. In this study, the molecular basis of Escherichia coli O157:H7 and Salmonella enterica serovar Typhimurium flagella binding to epithelial cell cultures was investigated. Flagella interactions with host cell surfaces were intimate and crossed cellular boundaries as demarcated by actin and membrane labelling. Scanning electron microscopy revealed flagella disappearing into cellular surfaces and transmission electron microscopy of S. Typhiumurium indicated host membrane deformation and disruption in proximity to flagella. Motor mutants of E. coli O157:H7 and S. Typhimurium caused reduced haemolysis compared to wild-type, indicating that membrane disruption was in part due to flagella rotation. Flagella from E. coli O157 (H7), EPEC O127 (H6) and S. Typhimurium (P1 and P2 flagella) were shown to bind to purified intracellular components of the actin cytoskeleton and directly increase in vitro actin polymerization rates. We propose that flagella interactions with host cell membranes and cytoskeletal components may help prime intimate attachment and invasion for E. coli O157:H7 and S. Typhimurium, respectively.

Methylation of Salmonella Typhimurium flagella promotes bacterial adhesion and host cell invasion.

The long external filament of bacterial flagella is composed of several thousand copies of a single protein, flagellin. Here, we explore the role played by lysine methylation of flagellin in Salmonella, which requires the methylase FliB. We show that both flagellins of Salmonella enterica serovar Typhimurium, FliC and FljB, are methylated at surface-exposed lysine residues by FliB. A Salmonella Typhimurium mutant deficient in flagellin methylation is outcompeted for gut colonization in a gastroenteritis mouse model, and methylation of flagellin promotes bacterial invasion of epithelial cells in vitro. Lysine methylation increases the surface hydrophobicity of flagellin, and enhances flagella-dependent adhesion of Salmonella to phosphatidylcholine vesicles and epithelial cells. Therefore, posttranslational methylation of flagellin facilitates adhesion of Salmonella Typhimurium to hydrophobic host cell surfaces, and contributes to efficient gut colonization and host infection.

13C-Metabolic Flux Analysis in Developing Flax (Linum usitatissinum L.) Embryos to Understand Storage Lipid Biosynthesis.

Flax (Linum usitatissinum L.) oil is an important source of α-linolenic (C18:3 ω-3). This polyunsaturated fatty acid is well known for its nutritional role in human and animal diets. Understanding storage lipid biosynthesis in developing flax embryos can lead to an increase in seed yield via marker-assisted selection. While a tremendous amount of work has been done on different plant species to highlight their metabolism during embryo development, a comprehensive analysis of metabolic flux in flax is still lacking. In this context, we have utilized in vitro cultured developing embryos of flax and determined net fluxes by performing three complementary parallel labeling experiments with 13C-labeled glucose and glutamine. Metabolic fluxes were estimated by computer-aided modeling of the central metabolic network including 11 cofactors of 118 reactions of the central metabolism and 12 pseudo-fluxes. A focus on lipid storage biosynthesis and the associated pathways was done in comparison with rapeseed, arabidopsis, maize and sunflower embryos. In our hands, glucose was determined to be the main source of carbon in flax embryos, leading to the conversion of phosphoenolpyruvate to pyruvate. The oxidative pentose phosphate pathway (OPPP) was identified as the producer of NADPH for fatty acid biosynthesis. Overall, the use of 13C-metabolic flux analysis provided new insights into the flax embryo metabolic processes involved in storage lipid biosynthesis. The elucidation of the metabolic network of this important crop plant reinforces the relevance of the application of this technique to the analysis of complex plant metabolic systems.

Cloning and molecular characterization of three lysophosphatidic acid acyltransferases expressed in flax seeds.

In the context of the growing demand for α-linolenic acid due to its high nutritional value as a polyunsaturated fatty acid, we have investigated the contribution of 2-lysophosphatidic acid acyltransferase (LPAAT) enzymes from flax (Linum usitatissimum) in the accumulation of α-linolenic acid into the oil fraction of flax seed. We have isolated the cDNAs encoding three class A microsomal LPAAT2 isoforms from developing flax seeds. The three isoforms, denominated LPAAT2A, LPAAT2A2 and LPAAT2B, are able to complement the LPAAT deficient JC201 E. coli mutant, confirming their functionality. We have performed enzymatic assays showing that the specific activity of the LPAAT2A isoform is significantly higher than that of the LPAAT2A2 and LPAAT2B toward the unsaturated oleic, linoleic and linolenic acids. Moreover, LPAAT2A presents in vitro a high specificity and selectivity for linoleic and linolenic acids as compared to saturated fatty acids. The three isoforms are expressed during all the stages of seed development and in stem and leaf tissues, as shown by an analysis of the transcription level of the corresponding genes. The heterologous expression of LPAAT2A in Arabidopsis seeds leads to an increase in the accumulation of linoleic and linolenic acids in the oil fraction of the seeds from two transgenic lines.

Cytocompatibility of Molecularly Imprinted Polymers for Deodorants: Evaluation on Human Keratinocytes and Axillary-Hosted Bacteria.

Molecularly imprinted polymers (MIPs), often dubbed "synthetic antibodies", can recognize and bind their target molecule with high affinity and selectivity, making them serious competitors with regard to biological antibodies. MIPs have gained popularity in various clinical applications and have even been applied in vivo. However, only a few studies on the biocompatibility of MIPs have been reported. Herein, we investigate on an example of a MIP that has proved its efficacy as an active agent to suppress body odors in cosmetic formulations, its effect on the viability and irritation potential of human epithelial cells. Since body odors are caused by bacteria present on the skin, bactericides are regularly added to deodorants sold on the market. However, there is growing anxiety concerning these bactericides as they can generate resistant bacteria, a problem for human and animal health. Therefore, we also assessed whether the MIP perturbs the resident skin bacteria, which were isolated from human sweat. Our results show that MIPs do not affect bacterial growth when cultured in liquid media, suggesting that they will not affect the skin flora, which protects the body from dangerous pathogens. This thorough in vitro toxicological assessment shows the biocompatibility of MIPs and constitutes a step further in their future consideration within cosmetic or pharmaceutical formulations for skin applications.

Untargeted Analysis of Semipolar Compounds by LC-MS and Targeted Analysis of Fatty Acids by GC-MS/GC-FID: From Plant Cultivation to Extract Preparation.

The way plants are grown and samples are harvested, prepared, and extracted has a profound impact on the output of a metabolomics experiment. In this chapter, we detail the experimental procedures from plant cultivation to extract preparation, in order to avoid difficulties that could result in contamination or undesired changes of the analytes. Two plant organs are mentioned as examples: tomato fruits (Solanum lycopersicum) and flax seeds (Linum usitatissimum). Extractions designed for the untargeted analysis of semipolar compounds by liquid chromatography-mass spectrometry (LC-MS) and targeted analysis of fatty acids by gas chromatography-mass spectrometry (GC-MS) or gas chromatography with flame ionization detector (GC-FID) are described.

Alternate thermoregulation and functional binding of Escherichia coli type 1 fimbriae in environmental and animal isolates.

Type 1 fimbriae (T1F) are well characterised cell surface organelles expressed by Escherichia coli and required for adherence to mannosylated host tissue. They satisfy molecular Koch's postulates as a virulence determinant and a host-adapted role has been reinforced by reports that T1F expression is repressed at submammalian temperatures. Analysis of a group of 136 environmental and animal E. coli isolates that express T1F at 37°C showed that 28% are also capable of expression at 20°C, in a phase variable manner. The heterogeneous proportions varied widely, and although growth temperature impacted the total proportion expressing T1F, there was no direct correlation between growth at 37°C and 20°C, indicative of differences in thermoregulation of the genetic switch (fimS) that controls phase variation. Specificities of the adhesin (FimH) also varied between the isolates: most bound to α-(1-3) mannan and yeast extracts as expected, but some recognised ß-(1-4)-mannans and N-linked glycoproteins from plants, and T1F from two of the isolates mediated binding to plant roots. The results expand our view of a well-described adherence factor to show alternative expression profiles and adhesin specificities, which in turn may confer an advantage for certain isolates in alternative hosts and habitats.

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.

Acylcarnitines participate in developmental processes associated to lipid metabolism in plants.

MAIN CONCLUSION: Plant acylcarnitines are present during anabolic processes of lipid metabolism. Their low contents relatively to the corresponding acyl-CoAs suggest that they are associated to specific pools of activated fatty acids. The non-proteinaceous amino acid carnitine exists in plants either as a free form or esterified to fatty acids. To clarify the biological significance of acylcarnitines in plant lipid metabolism, we have analyzed their content in plant extracts using an optimized tandem mass spectrometry coupled to liquid chromatography method. We have studied different developmental processes (post-germination, organogenesis, embryogenesis) targeted for their high requirement for lipid metabolism. The modulation of the acylcarnitine content was compared to that of the lipid composition and lipid biosynthetic gene expression level in the analyzed materials. Arabidopsis mutants were also studied based on their alteration in de novo fatty acid partitioning between the prokaryotic and eukaryotic pathways of lipid biosynthesis. We show that acylcarnitines cannot specifically be associated to triacylglycerol catabolism but that they are also associated to anabolic pathways of lipid metabolism. They are present during membrane and storage lipid biosynthesis processes. A great divergence in the relative contents of acylcarnitines as compared to the corresponding acyl-CoAs suggests that acylcarnitines are associated to very specific process(es) of lipid metabolism. The nature of their involvement as the transport form of activated fatty acids or in connection with the management of acyl-CoA pools is discussed. Also, the occurrence of medium-chain entities suggests that acylcarnitines are associated with additional lipid processes such as protein acylation for instance. This work strengthens the understanding of the role of acylcarnitines in plant lipid metabolism, probably in the management of specific acyl-CoA pools.

Early detection of colonic dysplasia by magnetic resonance molecular imaging with a contrast agent raised against the colon cancer marker MUC5AC.

Human gastric mucin MUC5AC is secreted in the colonic mucus of cancer patients and is a specific marker of precancerous lesions called aberrant crypt foci. Using MUC5AC as a specific marker can improve sensitivity in the detection of early colorectal cancer. Here we demonstrated that the accumulation of MUC5AC in xenograft and mouse stomach can be detected by magnetic resonance imaging (MRI). We used ultrasmall particles of iron oxide (USPIOs) conjugated with disulfide constrained heptapeptide that were identified using a screening phage display. To accomplish this, we employed positive selection of the phage display library on MUC5AC purified from fresh human colonic adenomas in combination with negative selection of the phage library on purified human MUC2, which is predominantly found in normal colorectal tissues. This conjugate was tested on human colorectal cancer cell lines that were either able or unable to secrete MUC5AC, both in vitro and in vivo. MUC5AC-USPIO contrast agent and USPIOs alone were not detected in cell lines unable to secrete MUC5AC. A combination of MRI and microscopy studies was performed to detect a specific accumulation of the contrast agent in vivo. Thus, the MUC5AC contrast agent enabled non-invasive detection of precancerous lesions and colorectal cancer, highlighting its potential use in diagnostics, in the early detection of colorectal cancer recurrences after treatment and in mechanistic studies implicating MUC5AC. Copyright © 2016 John Wiley & Sons, Ltd.

Alteration or adaptation, the two roads for human gastric mucin glycosylation infected by Helicobacter pylori.

Helicobacter pylori is a Gram-negative bacterium that colonizes the mucus niche of the gastric mucosa and infects more than half of the world's human population. Chronic infection may cause gastritis, duodenal ulcer, intestinal metaplasia or gastric cancer. In the stomach, H. pylori interacts with O-glycans of gastric mucins but the mechanism by which the bacteria succeed in altering the mucosa remains mainly unknown. To better understand the physiopathology of the infection, inhibitory adhesion assays were performed with various O-glycans expressed by human gastric mucins, and topographic expression of gastric mucins MUC5AC and MUC6 was analyzed for healthy uninfected individuals, for infected asymptomatic individuals and for patients infected by H. pylori and having the incomplete type of intestinal metaplasia. The glycosylation of the gastric mucosa of asymptomatic individuals infected by H. pylori was determined and compared with the glycosylation pattern found for patients with the incomplete type of intestinal metaplasia. Results show that H. pylori manages to modulate host's glycosylation during the course of infection in order to create a favorable niche, whereas asymptomatic infected individuals seem to counteract further steps of infection development by adapting their mucus glycosylation.