Escherichia coli cell components

In their natural environment, bacterial cells need to adapt to a wide range of osmotic conditions. Escherichia coli cells exposed to hypo-osmotic shock respond by a rapid release of cellular osmolytes such as proline, potassium glutamate, trehalose, and ATP. This ability prevents the cells from lysis by decreasing the turgor pressure on the challenge of a sudden shift in osmolarity. Bacterial MS channels, MscL and MscS (Fig. la and b), are major components of adaptation mechanisms to hypo-osmotic shock. Being located in the cytoplasmic membrane, MscL and MscS are activated by an increase of membrane tension... 

Renault et al. have demonstrated that DNP enhances the spectroscopic sensitivity of solid-state NMR measurements of uniformly ( C, N)-labelled preparations of Escherichia coli cells by more than an order of magnitude." It has been shown that the major molecular components in the cells can be characterized in this way. 

FIGURE 11.22 If the cell walls of bacteria such as Escherichia coli are partially digested and the cells are then osmotlcally shocked by dilution with water, the contents of the cells are extruded to the exterior. In electron micrographs, the most obvious extruded component is the bacterial chromosome, shown here surrounding the cell. (Dr. Gopal Murti/CNRI/Phototakr NYC)... 

Resistance to phagocytosis is sometimes associated with specific components of the cell wall and/or with the presence of capsules surrounding the cell wall. Classic examples of these are the M-proteins of the streptococci and the polysaccharide capsules of pneumococci. The acidic polysaccharide K-antigens of Escherichia coli and Sal typhi behave similarly, in that (i) they can mediate attachment to the intestinal epithelial cells, and (ii) they render phagocytosis more difficult. Generally, possession of an extracellular capsule will reduce the likelihood of phagocytosis. 

Most frequently, extracts of either prokaryotic or eukaryotic origin as such from Escherichia coli, wheat germ or rabbit reticulocytes are employed for cost reasons and availability. While those based on E. coli are unable of post-translational protein modification, eukaryotic extracts do allow synthesis of glycosylated or phosphorylated proteins to some extent when additional components, such as microsomes for glycosylation are added. Care needs to be taken with cell-free systems recombinated from the individual components when a native protein is to be produced that does not fold spontaneously... 

Schroten, H., Hanisch, F. G., Plogmann, R., Hacker, J., Uhlenbruck, G., Nobis-Bosch, R., and Wahn, V. (1992). Inhibition of adhesion of S-fimbriated Escherichia coli to buccal epithelial cells by human milk fat globule membrane components A novel aspect of the protective function of mucins in the nonimmunoglobulin fraction. Infect. Immun. 60,2893-2899. 

Since cinnamyl aldehyde is the main component of cassia oil (approximately 90%) and Sri Lanka cinnamon bark oil (approximately 75%) [49], it is industrially more important to generate cinnamyl alcohol, which is less abundantly available from nature but is important as cinnamon flavour, by biotransformation of natural cinnamyl aldehyde than vice versa. Recently, a whole-cell reduction of cinnamyl aldehyde with a conversion yield of 98% at very high precursor concentrations of up to 166 g L was described [136]. Escherichia coli DSM 14459 expressing a NADPH-dependent R alcohol dehydrogenase from Lactobacillus kefir and a glucose dehydrogenase from Thermoplasma acidophilum for intracellular cofactor regeneration was applied as the biocatalyst (Scheme 23.8). 

Macaloney, G. Hall, J.W. Rollins, M.J. Draper, I. Anderson, K.B. Preston, J. Thompson, B.G. McNeil, B., The utility and performance of near-infrared spectroscopy in simultaneous monitoring of multiple components in a high cell density recombinant Escherichia coli production process Bioprocess Eng. 1997, 17, 157-167. 

A possible application for nanotubes (see Section 16.2) is in the sensing and decontamination of chemical and biological weapons. Preliminary results [976] show that some lipid nanotubes change colour when exposed to model chemical weapon components and bacteria, and that they may be able to reduce the concentrations of bacteria. Figure 16.5 shows nanotubes adsorbing onto and even piercing an Escherichia coli bacteria cell. 

The initial emphasis in analytical biotechnology was on broad safety concerns that translated into detection of host-cell components such as DNA, endotoxins, Escherichia colt proteins, and retroviral contamination.2 The detection of these impurities requires development of high-sensitivity assays that are based primarily on antibodies [e.g., enzyme-linked immunosorbent assay (ELISA) for E. coli proteins) or radioactivity (e.g., dot-blot assays for DNA detection). New developments are focused on low-sensitivity detection, characterization, and removal of undesirable target sequence variants. Bioseparations play an important role even after a product has been isolated and shown to contain a low level of contaminants for initiation of clinical studies. The focus shifts to achievement of a reproducible, large-scale manufacturing process. At this stage, analytical methods provide essential informa-... 

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