Microbial pathogens, interaction

Phalipon A, Sansonetti PJ Microbial-host interactions at mucosal sites. Host response to pathogenic bacteria at mucosal sites. Curr Top Microbiol Immunol 1999 236 163-189. 

It is now known that the initial interaction between plants and bacteria of the Rhizobiaceae is a chemical detection by the microbe of a susceptible host, i.e., the host produces compounds which act as signals for the microbial pathogen or symbiont. The microbe responds to these signals by expression of genes necessary in subsequent stages of the interaction. For a few of the Rhizobiaceae some signal compounds involved have been identified (1-7). 

TSome microbial pathogens have lectins that mediate bacterial adhesion to host cells or toxin entry into cells. The bacterium believed responsible for most gastric ulcers, Helicobacter pylori, adheres to the inner surface of the stomach by interactions between bacterial membrane lectins and specific oligosaccharides of membrane glycoproteins of the gastric epithelial cells... 

Sturz, A.V., Carter, M.R., Johnston, H.R. A review of plant disease, pathogen interactions and microbial antagonism under conservation tillage in temperate humid agriculture. Soil Till Res 1997 41 169-189. 

Because they are easily accessible, glycans displayed on the surface of mammalian cells provide enormous opportunities to bind to many microbial pathogens, ranging from viruses to molecular toxins and from pathogenic bacteria to parasites. In multivalent binding, multiple interactions between ligands and various receptors are common (Fig. 16.1). One representative example is ricin—a versatile and durable A-B-type toxin—in which one of the protein chains (the B chain) is a lectin that interacts and binds terminal galactose (Gal) on the surface of eukaryotic cells with multivalent interactions to facilitate entry of the other peptide chain (the A chain) into the cell to cause cellular death via the catalytic... 

Microbial pathogens utilize different types of lectins for targeting the glycans on the surface of host cells. Many bacteria are covered with pili or fimbriae that contain a very special class of lectins known as adhesins because they play a role in attachment to epithelial cells. These lectins are monomeric and comprise only one binding site. Because the adhesins are repeated on the pilus, a larger number of adhesins on the bacterial surface create multivalent interaction with the host glycans. 

Plant cuticle, the boundary layer at v hlch microbial pathogens come into contact with the plant, is derived entirely from lipids. Obviously, the cuticle can play an Important role in the interaction between the microbe and the host plant. The cuticle is composed of an Insoluble structural polymer called... 

During blood contact with any foreign material, several components in the blood are activated through a variety of enzymatic and cellular processes. In the setting of chronic hemodialysis with up to 15 h of weekly blood—material interactions, the immune system, in particular, appears to be in a constantly activated, inflammatory state. Some have su ested the high incidence of infection and septicemia in these patients is due, in part, to the activated immune system s inability to adequately respond to microbial pathogens. Therefore, the search for more biocompatible materials for hemodialysis and hemoperfusion is of great importance. 

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