Polysaccharide

Summary

Polysaccharides (ˌpɒliˈsækəraɪd), or polycarbohydrates, are the most abundant carbohydrates found in food. They are long-chain polymeric carbohydrates composed of monosaccharide units bound together by glycosidic linkages. This carbohydrate can react with water (hydrolysis) using amylase enzymes as catalyst, which produces constituent sugars (monosaccharides, or oligosaccharides). They range in structure from linear to highly branched. Examples include storage polysaccharides such as starch, glycogen and galactogen and structural polysaccharides such as cellulose and chitin. Polysaccharides are often quite heterogeneous, containing slight modifications of the repeating unit. Depending on the structure, these macromolecules can have distinct properties from their monosaccharide building blocks. They may be amorphous or even insoluble in water. When all the monosaccharides in a polysaccharide are the same type, the polysaccharide is called a homopolysaccharide or homoglycan, but wh

Official source

https://en.wikipedia.org/wiki/Polysaccharide

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FIBCD1 Binds Aspergillus fumigatus and Regulates Lung Epithelial Response to Cell Wall Components

Lalit Kumar Dubey

Aspergillus fumigatus (A. fumigatus) is a ubiquitous fungus of clinical importance associated with development of various pulmonary diseases and allergic hypersensitivity reactions. It is protected against environmental stress by a cell wall that contains polysaccharides such as chitin. We previously demonstrated that fibrinogen C domain-containing protein 1 (FIBCD1) is a membrane-bound protein that binds chitin through a conserved S1 binding site and is expressed in intestinal epithelium and salivary glands. Here, we further localized FIBCD1 protein expression at the surface of bronchial and alveolar human lung epithelium, observed recognition of A. fumigatus cell wall with S1 site-independent recognition. We observed FIBCD1-mediated suppression of IL-8 secretion, mucin production, and transcription of genes associated with airway inflammation and homeostasis in FIBCD1-transfected lung epithelial cells. These modulations were generally enforced by stimulation with A. fumigatus cell wall polysaccharides. In parallel, we demonstrated a FIBCD1-mediated modulation of IL-8 secretion induced by TLR2, -4, and -5. Collectively, our findings support FIBCD1 as a human lung epithelial pattern recognition receptor that recognizes the complex A. fumigatus cell wall polysaccharides and modulates the lung epithelial inflammatory response by suppressing inflammatory mediators and mucins.

FRONTIERS MEDIA SA2018

Model for random hydrolysis and end degradation of linear polysaccharides: application to the thermal treatment of mannan in solution

Albert Renken

The kinetics for homogeneous hydrolysis of mannan was studied in a batch reactor at temps. from 160 to 220 Deg. A formate buffer ensured a pH of 3.8-4.0, measured at 25 Deg. Samples were analyzed for oligosaccharides at a d.p. of ?6 and also for the total amt. of mannose after acid hydrolysis. A math. model with 2 reactions, i.e., (1) random hydrolysis of the glucosidic bonds; and (2) degrdn. of the reducing end of the mol., describes accurately the time course of oligosaccharides. Optimized rate consts. follow closely an Arrhenius relationship, with the degrdn. having a higher activation energy (140 kJ/mol) than the hydrolysis (113 kJ/mol). The math. model has the advantage that prodn. of small mols. is independent of the initial chain-length distribution, as long as the av. initial chain length is some 5 times longer than the largest species measured. It can be applied to 1st-order depolymn. of other linear polymers with 1 link type in order to det. reaction rate consts. or make predictions about mol. wt. distribution on the base of known reaction rate consts. [on SciFinder (R)]

1999

During infection, microbial pathogens encounter phagocytic cells of the host innate immune system, such as macrophages and neutrophils. These encounters typically lead to uptake and killing of the bacteria by the host cell or, conversely, parasitization of the host cell by the bacteria. Microscopic analysis of these host-microbe interactions is complicated by the fact that phagocytic cells are motile and tend to stray out of the field of view. Most host-pathogen studies have therefore been undertaken at the population level. However, the success of many pathogens likely lies in their ability to generate heterogeneity within the population, facilitating adaptation to every host micro-environment and to environmental perturbations (such as application of an antibiotic). We believe that studying host-pathogen interactions at the single-cell level can reveal not only new mechanisms of pathogenesis but also why current treatments are not always successful. This thesis presents a novel microfluidic device for the long-term co-culturing of phagocytic cells and bacteria within spatially confining microchambers. Each device is patterned with thousands of microchambers, permitting high-throughput fluorescence timelapse microscopy of host-microbe interactions at single-cell resolution. We demonstrate the utility of this approach by co-culturing an established host-cell model, Dictyostelium discoideum, with the extracellular pathogen Klebsiella pneumoniae. We observed that K. pneumoniae is readily taken up and killed by D. discoideum but some events can take ten times as long as others. The capsule, a polysaccharide layer present at the surface at the bacterial cell wall, reduces the phagocytosis efficiency by 1.5 fold, but does not influence the killing time. The opportunistic human pathogen Mycobacterium marinum was then used to study intracellular bacterial virulence. As expected, bacteria could infect host cells, replicate inside, and eventually lyse them. However, surprisingly, in the majority of the infections, the bacteria were actually released from the host, with no apparent harm to either the host or the bacteria. Less frequently, bacteria were even seen being killed. The timing of these events was highly heterogeneous, ranging from a couple of hours to several days. In summary, the tools presented in this thesis provide a new and simple approach for following individual host-microbe interactions at high spatiotemporal resolution from the onset to the end of infections. This work unveiled that the timing and outcome of host-microbe interactions are unexpectedly heterogeneous, which may have important consequences for the bacterial pathogenesis and ultimately for the development of future treatment of microbial infections.

EPFL2016