Cell wall constituent

Agar occurs as a cell-wall constituent of the red marine algae Rho ophyceae, from which it is extracted by hot water, and marketed as a dry powder, flakes, or strips. It dissolves in hot water and sets on cooling to a jelly at a concentration as low as 0-5%. Its chief uses are as a solid medium for cultivating micro-organisms, as a thickener, emulsion stabilizer in the food industry and as a laxative. 

Endotoxin and Muramyl Dipeptide Derivatives. Bacterial cell wall constituents such as the Hpopolysaccharide endotoxin and muramyl dipeptide, which stimulate host defense systems, show radioprotective activity in animals (204). Although endotoxin is most effective when given - 24 h before irradiation, it provides some protection when adrninistered shortiy before and even after radiation exposure. Endotoxin s radioprotective activity is probably related to its Hpid component, and some of its properties may result from PG and leukotriene induction (204). 

Pectin as one of the major plant cell wall constituents has received much attention both from a scientific and a technological point of view. Although pectin has been known to be a very complex heteropolysaccharide for quite some time, most progress on the elucidation of its structure has been attained in the last decade as a result of refinement and development of new more powerful techniques like HPAEC, HPGPC, NMR and the application of purified enzymes able to degrade specific parts of the complex molecule. 

Hahn M. G., Bucheli P., Cervone F., Doares S. H., O Neill R. A., Darvill A. Albersheim P. (1989). Roles of cell wall constituents in plant-pathogen interactions. In Nester E. Kosuge T., ed. Plant Microbe Interactions, Vol. 4. McGraw-Hill Publishing Co., 131-181. 

Like all bacteria, actinomycetes are prokaryotic microorganisms. In addition, the adenine-thymine and guanine-cytosine contents of bacteria and actinomycetes are similar, as are the cell wall constituents of both types of microorganisms. Actinomycetes filaments are also about the same size as those of bacteria. 

An understanding of relationships between cell wall constituents and wall biodegradation is of particular importance to the economics of animal production since low digestibility of forages is associated with reduced intake. Such an understanding is also important in elucidating the role of fiber in human nutrition and of the decomposition of organic matter in soil. 

Method 7.5. Determination of neutrai detergent fibre (NDF) or plant cell-wall constituents... 

This is based on the method by Van Soest and Wine (1967) which has been modified according to subsequent recommendations. It is the only fibre determination suitable for non-ruminants. The residue consists of the plant cell-wall constituents cellulose, hemicellulose, lignin, cutin, NDF-insoluble tannin and ash. See the article by Cherney (2000) for current modifications these include the use of amylase to aid in the removal of starch from forages containing grain (Van Soest et al., 1991), which has been adopted by MAFF... 

Van Soest, P.J. and Wine, R.H. (1967) Use of detergents in the analysis of fibrous feeds. IV. Determination of plant cell-wall constituents. Journal of the Association of Official Analytical Chemists 50(1), 50-55. 

Bacitracin inhibits the dephosphorylation of this lipid carrier, a step essential to the carrier molecule s ability to accept cell wall constituents for transport. 

Enzyme Treatment. There are a number of enzymes which hydrolyze the microbial cell wall constituents. Enzymes exhibiting these activities include lysozyme, enzyme from snail extract and lytic enzyme systems of microbial origin composed of proteases,... 

A recently published book provides an excellent survey of issues that relate to contamination with endotoxins (present in both viable and nonviable bacteria), their released cell wall constituents, and also viable bacteria in the pharmaceutical industry [1]. It is important to know both the content of the work environment (e.g., indoor air) and the pharmaceutical products themselves. The former provides information on possible sources of microbial contamination and the latter the purity of the final commercial product (or precursors in various stages in its preparation). In some cases it is vital to know the actual bacterial species involved in contamination culture-based methods are standard microbiological techniques which were the focus of Jimenez [1] and thus will not be discussed further. Any contamination (e.g., with endotoxins), regardless of the species of origin, is of utmost of importance (e.g., in determining the safety of a batch of antibiotics to be administered intravenously). This is determined optimally by non-culture-based methods. 

Chitin is the microfibrillar component of some fungal cell walls and is equivalent to cellulose microfibrils in plants. It is a characteristic feature of the Ascomycetes, Deuteromycetes and Basidiomycetes but is absent in the Phycomycetes, which contain cellulose as their major cell wall constituent. 

Polyoxins are inhibitors of chitin biosynthesis. Chitin is a component of fungal cell walls except in Phycomycete fungi these contain cellulose as their major cell wall constituent, hence polyoxins are inactive against Plasmopara, Pythium and Phytophthora. 

Lignin is a complex phenolic cell wall polymer that is chemically cross-linked with hemicellulose and cell wall proteins. Most of the methods to determine lignin content are based on the removal of all other cell wall constituents, typically through acid hydrolysis, which will readily remove hemicellulose under mild conditions, and non-crystalline cellulose under more severe conditions. Several different methods will be discussed below. The different methods have also been extensively reviewed and compared by Hatfield et al. (1994), Brinkmann et al. (2002), Fukushima and Hatfield (2004), and Hatfield and Fukushima (2005). 

Out of 364 other tested enterobacteria 3 E. coli strains were positive, as were 8 of 9 Candida yeast isolates. These findings are not surprising because reciprocal cross-reactions between Salmonella Cl and some E. coli strains are well known (26) and in yeasts a mannan consisting of an a,l- -6 linked poly-D-mannose backbone with branches of a,l->-2 and a,l- -3 linked D-mannose residues is a principal cell-wall constituent (27). 

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