Measurements of the binding force between the Helicobacter pylori adhesin BabA and the Lewis b blood group antigen using optical tweezers

Interference of Lactiplantibacillus plantarum with Pseudomonas aeruginosa on the infected burns in Wistar rats

Burns are the most prevalent type of trauma in the world, and they have a high fatality rate. For cutaneous wound healing, modern and natural therapies, particularly probiotic supplements, have lately been considered. The goal of this study was to see how Lactiplantibacillus plantarum affected wound healing as well as the antibacterial activity of probiotic lactobacilli against Pseudomonas aeruginosa. The glass slide method was used to assess anti-adhesion activity, and the HPLC method was used to quantify anti-adhesion chemicals in cell-free supernatant (CFS). MDR P. aeruginosa was administered subcutaneously directly on the burn after induction of second-degree wounds. Three groups of animals were created. Every day, the supernatants were sprayed for therapy, and the wound healing was monitored. Lactobacilli bacteria had good anti-adhesion effects on P. aeruginosa, according to our findings, and HPLC research revealed that their inhibitory effect could be attributable to four main organic acids: lactic acid, acetic acid, citric acid, and succinic acid. When the effect of treatments on fibroblastic cells was examined, it was discovered that the group treated with L. plantarum supernatants had the most fibroblastic cells when compared to the non-treated group. Furthermore, the bacteria increased the number of fibroblastic cells, re-epithelialization in the wound area, and the thickness of the epidermis and dermis layers. Lactobacilli bacteria's antimicrobial activity against MDR P. aeruginosa was determined by prevents infection. These findings revealed that L. plantarum can treat a P. aeruginosa infection in a second-degree burn and can significantly reduce inflammation.

Force interactions between Yersiniae lipopolysaccharides and monoclonal antibodies: An optical tweezers study

This article reports the force spectroscopy investigation of interactions between lipopolysaccharides (LPSs) of two species from Yersinia genus and complementary (or heterologous) monoclonal antibodies (mAbs). We have obtained the experimental data by optical trapping on the "sensitized polystyrene microsphere - sensitized glass substrate" model system at its approach - retraction in vertical plane. We detected non-specific interactions in low-amplitude areas on histograms mainly due to physicochemical properties of abiotic surface and specific interactions in complementary pairs "antigen - antibodies" in high-amplitude areas (100-120 pN) on histograms. The developed measurement procedure can be used for detection of rupture forces in other molecular pairs.

Glycan–glycan interactions determine Leishmania attachment to the midgut of permissive sand fly vectors

Force spectroscopy was used to measure the adhesion of Leishmania to synthetic mimics of galectins on the sand fly midgut.

The Role of Glycans in Bacterial Adhesion to Mucosal Surfaces: How Can Single-Molecule Techniques Advance Our Understanding?

Bacterial adhesion is currently the subject of increased interest from the research community, leading to fast progress in our understanding of this complex phenomenon. Resent research within this field has documented the important roles played by glycans for bacterial surface adhesion, either through interaction with lectins or with other glycans. In parallel with this increased interest for and understanding of bacterial adhesion, there has been a growth in the sophistication and use of sensitive force probes for single-molecule and single cell studies. In this review, we highlight how the sensitive force probes atomic force microscopy (AFM) and optical tweezers (OT) have contributed to clarifying the mechanisms underlying bacterial adhesion to glycosylated surfaces in general and mucosal surfaces in particular. We also describe research areas where these techniques have not yet been applied, but where their capabilities appear appropriate to advance our understanding.

Genetic populations and virulence factors of Helicobacter pylori

Helicobacter pylori is a bacterium that has infected more than half of the human population worldwide. This bacterium is closely associated with serious human diseases, such as gastric cancer, and identifying and understanding factors that predict bacterial virulence is a priority. In addition, this pathogen shows high genetic diversity and co-evolution with human hosts. H. pylori population genetics, therefore, has emerged as a tool to track human demographic history. As the number of genome sequences available is increasing, studies on the evolution and virulence of H. pylori are gaining momentum. This review article summarizes the most recent findings on H. pylori virulence factors and population genetics.

Helicobacter pylori Adapts to Chronic Infection and Gastric Disease via pH-Responsive BabA-Mediated Adherence

The BabA adhesin mediates high-affinity binding of Helicobacter pylori to the ABO blood group antigen-glycosylated gastric mucosa. Here we show that BabA is acid responsive-binding is reduced at low pH and restored by acid neutralization. Acid responsiveness differs among strains; often correlates with different intragastric regions and evolves during chronic infection and disease progression; and depends on pH sensor sequences in BabA and on pH reversible formation of high-affinity binding BabA multimers. We propose that BabA's extraordinary reversible acid responsiveness enables tight mucosal bacterial adherence while also allowing an effective escape from epithelial cells and mucus that are shed into the acidic bactericidal lumen and that bio-selection and changes in BabA binding properties through mutation and recombination with babA-related genes are selected by differences among individuals and by changes in gastric acidity over time. These processes generate diverse H. pylori subpopulations, in which BabA's adaptive evolution contributes to H. pylori persistence and overt gastric disease.

Atomic force microscopy measurements reveal multiple bonds between Helicobacter pylori blood group antigen binding adhesin and Lewis b ligand

The strength of binding between the Helicobacter pylori blood group antigen-binding adhesin (BabA) and its cognate glycan receptor, the Lewis b blood group antigen (Le(b)), was measured by means of atomic force microscopy. High-resolution measurements of rupture forces between single receptor-ligand pairs were performed between the purified BabA and immobilized Le(b) structures on self-assembled monolayers. Dynamic force spectroscopy revealed two similar but statistically different bond populations. These findings suggest that the BabA may form different adhesive attachments to the gastric mucosa in ways that enhance the efficiency and stability of bacterial adhesion.

Assessing bacterial adhesion on an individual adhesin and single pili level using optical tweezers

Optical tweezers (OT) are a technique that, by focused laser light, can both manipulate micrometer sized objects and measure minute forces (in the pN range) in biological systems. The technique is therefore suitable for assessment of bacterial adhesion on an individual adhesin-receptor and single attachment organelle (pili) level. This chapter summarizes the use of OT for assessment of adhesion mechanisms of both non-piliated and piliated bacteria. The latter include the important helix-like pili expressed by uropathogenic Escherichia coli (UPEC), which have shown to have unique and intricate biomechanical properties. It is conjectured that the large flexibility of this type of pili allows for a redistribution of an external shear force among several pili, thereby extending the adhesion lifetime of bacteria. Systems with helix-like adhesion organelles may therefore act as dynamic biomechanical machineries, enhancing the ability of bacteria to withstand high shear forces originating from rinsing flows such as in the urinary tract. This implies that pili constitute an important virulence factor and a possible target for future anti-microbial drugs.

Optical manipulation for single-cell studies

In the last decade optical manipulation has evolved from a field of interest for physicists to a versatile tool widely used within life sciences. This has been made possible in particular due to the development of a large variety of imaging techniques that allow detailed information to be gained from investigations of single cells. The use of multiple optical traps has high potential within single-cell analysis since parallel measurements provide good statistics. Multifunctional optical tweezers are, for instance, used to study cell heterogeneity in an ensemble, and force measurements are used to investigate the mechanical properties of individual cells. Investigations of molecular motors and forces on the single-molecule level have led to discoveries that would have been difficult to make with other techniques. Optical manipulation has prospects within the field of cell signalling and tissue engineering. When combined with microfluidic systems the chemical environment of cells can be precisely controlled. Hence the influence of pH, salt concentration, drugs and temperature can be investigated in real time. Fast advancing technical developments of automated and user-friendly optical manipulation tools and cross-disciplinary collaboration will contribute to the routinely use of optical manipulation techniques within the life sciences.

Dynamic force spectroscopy of the Helicobacter pylori BabA-Lewis b binding

The binding strength of the Helicobacter pylori adhesin-receptor complex BabA-ABO/Lewis b has been analyzed by means of dynamic force spectroscopy. High-resolution measurements of rupture forces were performed in situ on single bacterial cells, expressing the high-affinity binding BabA adhesin, by the use of force measuring optical tweezers. The resulting force spectra revealed the mechanical properties of a single BabA-Leb bond. It was found that the bond is dominated by one single energy barrier and that it is a slip-bond. The bond length and thermal off-rate were assessed to be 0.86+/-0.07 nm and 0.015+/-0.006 s(-1), respectively.

Relevance of MUC1 mucin variable number of tandem repeats polymorphism in H pylori adhesion to gastric epithelial cells

AIM: To evaluate the influence of MUC1 mucin variable number of tandem repeats (VNTR) variability on H pylori adhesion to gastric cells.

METHODS: Enzyme linked immunosorbent assay (ELISA)-based adhesion assays were performed to measure the adhesion of different H pylori strains (HP26695 and HPTx30a) to gastric carcinoma cell lines (GP202 and MKN45) and GP202 clones expressing recombinant MUC1 with different VNTR lengths.

RESULTS: Evaluation of adhesion results shows that H pylori pathogenic strain HP26695 has a significantly higher (P < 0.05) adhesion to all the cell lines and clones tested, when compared to the non-pathogenic strain HPTx30a. Bacteria showed a significantly higher (P < 0.05) adhesion to the GP202 cell line, when compared to the MKN45 cell line. Furthermore, both strains showed a significantly higher (P < 0.05) adhesion to GP202 clones with larger MUC1 VNTR domains.

CONCLUSION: This work shows that MUC1 mucin variability conditions H pylori binding to gastric cells. The extent of bacterial adhesion depends on the size of the MUC1 VNTR domain. The adhesion is further dependent on bacterial pathogenicity and the gastric cell line. MUC1 mucin variability may contribute to determine H pylori colonization of the gastric mucosa.

A Method of Orthogonal Oligosaccharide Synthesis Leading to a Combinatorial Library Based on Stationary Solid-Phase Reaction

A new, efficient synthesis of oligosaccharides, which involves solid-phase reactions without mixing in combination with an orthogonal-glycosylation strategy, is described. Despite a great deal of biological interest, the combinatorial chemistry of oligosaccharides is an extremely difficult subject. The problems include 1) lengthy synthetic protocols required for the synthesis and 2) the variety of glycosylation conditions necessary for individual reactions. These issues were addressed and solved by using the orthogonal-coupling protocol and the application of a temperature gradient to provide appropriate conditions for individual reactions. Furthermore, we succeeded in carrying out solid-phase reactions with neither mechanical mixing nor flow. In this report, the synthesis of a series of trisaccharides, namely, alpha/beta-L-Fuc-(1-->6)-alpha/beta-D-Gal-(1-->2/3/4/6)-alpha/beta-D-Glc-octyl, is reported to demonstrate the eligibility of the synthetic method in combinatorial chemistry.

Method used to measure interaction of proteins with dual-beam optical tweezers

In the force measurement of protein-protein interaction, proteins are usually attached to microbeads, so the coated beads serve as both handles and force transducers. Due to the short interaction distance between proteins, the beads are usually close enough to each other. When dual-beam optical tweezers and quadrant photodiode detector are used to investigate the interaction of proteins, it is found that the signal of detected beads is greatly affected by adjacent beads. Analysis reveals that the contribution of two beads to the quadrant detector signal is independent. A method for extracting the real interaction signal from a disturbed one is presented. Based on this method, interaction between microtubules and AtMAP65-1 is measured. The results show that this method is useful for measuring short-distance interaction with the precision of piconewton and nanometer scales.

Helicobacter pylori adhesion to carbohydrates

Adherence of bacterial pathogens to host tissues contributes to colonization and virulence and typically involves specific interactions between bacterial proteins called adhesins and cognate oligosaccharide (glycan) or protein motifs in the host that are used as receptors. A given pathogen may have multiple adhesins, each specific for a different set of receptors and, potentially, with different roles in infection and disease. This chapter provides strategies for identifying and analyzing host glycan receptors and the bacterial adhesins that exploit them as receptors, with particular reference to adherence of the gastric pathogen Helicobacter pylori.

A sticky chain model of the elongation and unfolding of Escherichia coli P pili under stress

A model of the elongation of P pili expressed by uropathogenic Escherichia coli exposed to stress is presented. The model is based upon the sticky chain concept, which is based upon Hooke's law for elongation of the layer-to-layer and head-to-tail bonds between neighboring units in the PapA rod and a kinetic description of the opening and closing of bonds, described by rate equations and an energy landscape model. It provides an accurate description of the elongation behavior of P pili under stress and supports a hypothesis that the PapA rod shows all three basic stereotypes of elongation/unfolding: elongation of bonds in parallel, the zipper mode of unfolding, and elongation and unfolding of bonds in series. The two first elongation regions are dominated by a cooperative bond opening, in which each bond is influenced by its neighbor, whereas the third region can be described by individual bond opening, in which the bonds open and close randomly. A methodology for a swift extraction of model parameters from force-versus-elongation measurements performed under equilibrium conditions is derived. Entities such as the free energy, the stiffness, the elastic elongation, the opening length of the various bonds, and the number of PapA units in the rod are determined.