Cell envelope of bacteria

Alternatively, /cuptake, may represent the rate constant associated with transfers from immediately outside the cell to the interior spaces where the relevant enzymes occur. In this case, we need to focus on how long it takes for microorganisms to be equilibrated with medium in which they occur (step 1 in Fig. 17.1). This requires an evaluation of the time for chemicals to be transported from the outside of the microorganisms across their cell envelope to the relevant enzymes. The cell envelope of bacteria differs from species to species (Sikkema et al., 1995) and can even be changed by a single microbial strain in ways that affect cross-membrane transport in response to environmental conditions (e.g., Pinkart et al., 1996 Ramos et al., 1997). However, a general description is useful in the context of molecular... 

The cell envelopes of bacteria play an essential role in bacterial virulence, surface attachment and biofilm formation (O Toole et al, 2000). This cell compartment possesses PolyPs, and thereby its role in the above functions was intensively investigated. The conclusion was... 

Factors that might influence adhesion properties include the number of fimbriae per cell, the number of fimbriae that are functional for receptor binding, the fraction of cells that are fimbriated, the length and the flexibility of fimbriae, and the ability of fimbriae to deform under the influence of mechanical force. For example, it is up to date not known to what extent variant residues in the FimH receptor-binding domain affect assembly and thus the number of fimbriae on the bacterial cell envelope of bacteria expressing mutant FimH receptor-binding domains. The receptor-binding domain is necessary to initiate pilus assembly by interactions between... 

Cell envelopes of prokaryotic organisms (archaea and bacteria) are characterized by the presence of two distinct components the cytoplasmic membrane, which constitutes the inner layer, and an outer supramolecular layered cell wall (for reviews see Ref. 4), which pre-... 

Studies on S-layers present on the cell envelopes of a great variety of pathogenic organisms [100] revealed that these crystalhne arrays can represent important virulence factors. Most detailed studies have been performed on the fish pathogenic bacteria Aeromonas salmonicida and Aeromonas hydrophila [102] and the human pathogen Campylobacter fetus uh p. fetus [103] and Bacillus anthracis [104]. For example, whole-cell preparations or partially purified cell products are currently used as attenuated vaccines against various fish pathogens [102,105]. 

The observed adjuvanticity of Bordetella pertussis is largely attributable to the presence of pertussis toxin and lipopolysaccharide (LPS). LPS, a constituent of the cell envelope of Gramnegative bacteria (Chapter 3), essentially consists of polysaccharide moieties to which lipid (lipid A) is covalently attached. 

Figure A2.1 Schematic cross-sections of the cell envelopes of (a) Gram-positive and (b) Gramnegative bacteria...

Cell envelopes of archaea diifer distinctly from those of bacteria and show remarkable structural and chemical diversity. Murein, the typical sacculus-forming polymer of bacteria, and lipopolysaccharide-containing outer membranes, characteristic of gramnegative bacteria, are not found in archaea. Crystalline surface layers (S-layers) are common in both prokaryotic domains and they consist of protein or glycoprotein subunits (Table 1). However, S-layers in archaea have a form-stabilizing function especially when they are the only envelope layer outside the cytoplasmic membrane, while in bacteria S-layers have no distinct form-stabilizing function. 

One of the common surface structures of archea and bacteria are monomolecular crystalline arrays of protein subunits, called S-layers [106-109]. They constitute the outermost component of tlie cell envelope of these procaryotic organisms. S-layer subunits can be aligned in lattices with oblique, square, or hexagonal symmetry. Since S-layers are monomolecular assemblies of identical protein subunits, they exhibit pores of identical size and morphology. A group of nonclassical cell wall polymers, called secondary cell wall polymers (SCWPs), are attached noncova-lently, presumably by a lectin-type interaction, to the S-layer proteins. 

Peptidoglycans have been postulated as a possible causative agent for pulmonary inflammation associated with inhalation of Gm+ bacteria. Peptidoglycans are components of the cell wall envelope of bacteria and are especially prevalent in the backbone of Gm+ bacteria. They may act as endotoxin-like molecules when inhaled. Muramic acid is an amino sugar component of peptidoglycans that does not appear elsewhere in nature and is a suitable marker for analytical assays (Black et al., 1994 Fox et al., 1993 Fox et al., 1995 Sonesson et al., 1988). Although peptidoglycans have been found in hospital and home air conditioner filters (Fox and Rosario, 1994), to date there have been no systematic dose-response studies to identify their potency. 

Johansen, C., Verheul, A., Gram, L., Gill, T., and Ahee, T. 1997. Protamine-induced permeabilization of cell envelopes of gram-positive and gram-nt ative bacteria. Appl Environ. Microbiol 63, 1155-1159. 

Costerton, J. W. Structure and function of the cell envelope of Gram negative bacteria. Bac-teriolRev 1974, 38, 87-110. 

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