Microbial cell wall components

Furthermore, analytes involved in food immunoassays are of extremely different chemical nature, and are present in a very broad range of concentrations. Whereas macromolecules (such as protein, enzymes, polysaccharides, and microbial cell-wall components) are generally present in the mg per kg range, environmental contaminants, residues from farming practices, antibiotics, toxins, and pathogens are often present at much lower concentration, as low as 0.1 pg per kg. Food analytes for which immunoassays have been developed and are commercially available are listed in Table 1. 

Many different types of carbohydrate-containing molecules are located on the surface of microbial cells. Some of these are components of die microbial cell wall and are limited to certain types of micro-organisms such as bacterial peptidoglycan, lipopolysaccharides, techoic adds and yeast mannans. Other polysaccharides are not... 

Humic material does not appear to be a prominent component of this HMW fraction. The principal components appear to be proteins and sugars, particularly N-acetylamino sugars, which probably originate from the degradation of microbial cell walls. 

This review will address the structure and biosynthesis of important microbial cell wall polysaccharides, as well as chemical syntheses of these stmctures, and their roles in human diseases and disease treatments. The document is divided into sections discussing bacterial peptidoglycan, the Gram-negative outer membrane, corynebacterial cell wall components, and capsular antigens. 

Lytic enzyme systems provide a chemically mild, low-shear and catalytically specific alternative to mechanical cell disruption. Depending on the particular lytic system employed and its purity, the enzymes may be engineered to attack cell wall components alone, without product damage. The enzyme lysozyme, active against some bacterial cell walls, has been used to harvest bovine growth hormone granules from 12. coli (8), and a membrane-associated hydroxylase complex from . putida (11) use of other bacteriolytic enzymes from a variety of microbial sources have also been reported (3). 

The efficacy of a preservative and the concentration level of a microbicide to be added are very much dependent on the germ content of the material to be protected. This is in particular valid for electrophilic active microbicides which in general react irreversibly with nucleophilic components of the microbial cell, that means that they are used up by being effective. But membrane active microbicides which adsorptively coat microbial cell walls are also withdrawn from action at least temporarily if large numbers of microbial cells are present. The exponential growth profile of microbes (p. 2) always has to be taken into consideration. 

In response to exposure to an antigen, microorganisms and other living entities produce antibodies. Immunological techniques rely on the interaction between an antigen and an antibody specific for that antigen. The antigen may be a microbial cell wall or capsule, a characteristic cellular component, or even a specific metabolite. 

The classification of wastewater in terms of size distribution is normally done from a practical point of view. Typically, a distinction is made between soluble, colloidal and suspended components (Figure 3.6). While this definition for determining what solids are is rational as far as physical transport processes in sewers are concerned, when dealing with the microbial processes for sewer conditions, an extension of the solids definition is required. Particles larger than about 10-4 pm cannot be transported through the cell wall and are, therefore, from a microbial point of view, considered particles. 

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