Bacteria, cell walls composition

As IR analysis provides information on the bulk composition, the correlation with XPS data may be explained by the fact that in certain sets of Gram-positive strains, a variation of surface composition reflects the variation of the cell wall composition and that the cell wall represents a large proportion of the cell dry weight. This explanation is supported by the study of 5 different species of Gram-positive bacteria. The polypeptide surface concentration of the isolated cell walls deduced from XPS analysis was in excellent agreement with the polypeptide concentration determined by biochemical analysis. On the other hand. Bacillus brevis whole cells showed a twice higher surface concentration of polypeptides compared to that of fom coryneform bacteria, which was attributed to the presence of an S-layer. Consistently the polypeptide concentration of the cell wall of B. brevis was intermediate between that of whole cells of B. brevis and of cell walls and whole cells of the coryneform bacteria. This supports both the surface specificity of the XPS analysis... 

Heavy metals bound to bacteria-soil composites may not be as easily released to the environments as those sorbed by pure bacteria. Flemming et al. (1990) reported that the order of remobilization of heavy metals from bacteria-clay composites was Cr Ag < Cu. Chromium was veiy stable when sorbed by bacterial cell walls, clay, and bacterial wall-clay... 

Vecchio A, Finoli C, Simine DD, Andreoni V (1998) Heavy metal biosorption by bacterial cells. Fresenius J Anal Chem 361 338-342 Walker SG, Flemming CA, Ferris FG, Beveridge TJ, Bailey GW (1989) Physicochemical interaction of Escherichia coli cell envelopes and Bacillus subtilis cell walls with two clays and ability of the composite to immobililze heavy metals from solution. Appl Environ Microbiol 55 2976-2984 Wightman PG, Fein JB (2001) Ternary interactions in a humic acid-Cd-bacteria system. ChemGeol 180 55-65... 

Gram Stain A staining procedure used in classifying bacteria. A bacterial smear on a slide is stained with a purple basic triphenyl methane dye, usually crystal violet, in the presence of iodine/potassium iodide. The cells are then rinsed with alcohol or other solvent, and then counter-stained, usually with safranin. The bacteria then appear purple or red according to their ability to keep the purple stain when rinsed with alcohol. This property is related to the composition of the bacterial cell wall. 

Recent results indicate that not only topogenic signals and membrane composition contribute to the proper topology of a membrane protein. The antimicrobial peptide nisin, produced by Lactococcus lactis, kills Gram-positive bacteria via pore formation, thus leading to the permeabilisation of the membrane. Nisin depends on the cell-wall precursor Lipid II, which functions as a docking molecule to support a perpendicular stable transmembrane orientation [43]. 

Generalized representations of the internal structures of animal and plant cells (eukaryotic cells). Cells are the fundamental units in all living systems, and they vary tremendously in size and shape. All cells are functionally separated from their environment by the plasma membrane that encloses the cytoplasm. Plant cells have two structures not found in animal cells a cellulose cell wall, exterior to the plasma membrane, and chloroplasts. The many different types of bacteria (prokaryotes) are all smaller than most plant and animal cells. Bacteria, like plant cells, have an exterior cell wall, but it differs greatly in chemical composition and structure from the cell wall in plants. Like all other cells, bacteria have a plasma membrane that functionally separates them from their environment. Some bacteria also have a second membrane, the outer membrane, which is exterior to the cell wall. 

The correlation between chemical composition of microorganisms and their susceptibility to sakacin P, a bacteriocin produced by some lactic acid bacteria, was carried out by Oust et al. [53], It could be shown that at least some of the variations in the susceptibility to sakacin P in Listeria monocytogenes can be correlated to alterations in the chemical composition of the bacterial cell wall. 

Like plants, bacteria have a rigid cell wall. Hence appropriate measures are taken to weaken or break the cell wall before the cells are lysed for the extraction of RNA. Separate methods [10] exist for gram-negative or grampositive bacteria because of differences in their cell compositions. 

Bacterial membranes have a much more complex construction than mammalian membranes. This enables bacteria to survive in the various environments of host organisms. Knowledge of the composition and functioning of bacterial membranes is therefore essential to the development of anti-infective drugs. In order to be effective, antibacterial agents not only have to have optimal pharmacokinetic properties such as uptake and distribution in the patient, but they must also be able to cross an additional barrier, the cell wall of the bacteria, so that they can reach the target site. This additional barrier is remarkable on account of its rigidity and permeability. The construction and structural uniqueness of this barrier is briefly described below. 

Bacteria and archaea share many traits and it was not until the early 1980s that differences first became evident from analyses of gene sequences. One major difference is the composition of cell walls. A more striking contrast is in the structure of the lipids that make up their cytoplasmic membranes. Differences also exist in their respective patterns of metabolism. Most archaea are anaerobes, and are often found inhabiting extreme environments. It is possible that their unusual membrane structure... 

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