Host-bacterium interactions

Lipopolysaccharides are heat-stable complex amphiphilic macromolecules indispensable for the bacterial growth, viability and for the correct assembly of the external membrane they represent a defensive barrier which helps bacteria to resist to antimicrobial compounds and environmental stresses and are involved in many aspects of host-bacterium interactions as recognition, adhesion, colonization, and, in the case of extremophile bacteria, in the survival under harsh conditions (Alexander and Rietschel, 2001 Raetz and Whitfield, 2002 Raetz et al 2007). LPS are also called endotoxins because they are cell-bound and, once released, play a key role in the pathogenesis of Gram-negative infections, in mechanisms as... 

These results confirm that expression of IAA-genes alone is sufficient to initiate the development of knots on oleander, while cytokinins are necessary for the full expression of the disease symptoms (determining knot size). This finding also indicates that plant tissues (stems and leaves) react differently to various strains of the bacterium, and suggests that, besides phytohormones, other pathogenic factors could be involved in this host-pathogen interaction. The necrotic reaction of oleander leaves heavily inoculated with olive strains was interpreted as a possible form of hypersensitivity reaction [42]. 

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... 

The Rhizobium-legume symbiosis, an interaction between a prokaryote (Rhizobium) and a eukaryote (legume), requires a series of sequential induction and function of both bacterium-encoded (bac-teroidins) and host-encoded (nodulins) nodule-specific proteins. It has been shown that many plant (Peters et al., 1986 Firmin et al., 1986 Djordjevic et al., 1987 Sadowsky et al., 1988 see also Peters Verma,... 

FIGURE 16.1 Multivalent binding of a bacterium to the clustered carbohydrate ligand carrying matching terminal carbohydrate residue(s) found in the host cell surface. The multivalent interaction prevents the attachment of the bacterium to the host cell surface. The functional role of the linker is the optimal presentation of the glycan into the binding site of the receptor, but it may also be involved in additional hydrophobic contacts. 

Animals and plants constantly interact with bacteria present within their environment. For an infection to develop, such microorganisms must remain associated with the host and increase their numbers more rapidly than they can either be eliminated or killed. This balance relates to the ability of the bacterium to mobilize nutrients and multiply in the face of innate defences and a developing immune response by the now compromised host. 

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