Escherichia coli regulation

Sperandio V, Torres AG and Kaper JB. 2002. Quorum sensing Escherichia coli regulators B and C (QseBC) a novel two-component regulatory system involved in the regulation of flagella and motility by quorum sensing in E. coli. Mol Microbiol 43(3) 809-821. 

More than 30 years ago Jacob and Monod introduced the Escherichia coli lac operon as a model for gene regulation. The lac repressor molecule functions as a switch, regulated by inducer molecules, which controls the synthesis of enzymes necessary for E. coli to use lactose as an energy source. In the absence of lactose the repressor binds tightly to the operator DNA preventing the synthesis of these enzymes. Conversely when lactose is present, the repressor dissociates from the operator, allowing transcription of the operon. 

From a genetical point of view, Saccharomyces cerevisiae is an ideal organism which may be considered the Escherichia coli of eukaryotic cells [4,5]. This is true in particular for the study of metabolic regulation and for that of membrane transport [6]. Finally, the astonishing resemblance between many yeast proteins and certain mammalian-cell proteins has seriously broadened the scope of interest. Although a few reports have appeared on amino acid transport in some other yeasts, most investigations in this field have used strains of Saccharomyces cerevisiae. 

The conditions under which these function and their regulation depend on the organism. For example, in Escherichia coli, oxygen represses the synthesis of the other reductases, and under anaerobic conditions the reductases for fumarate, DMSO, and TMAO are repressed by nitrate. This does not apply to Wolinella succinogenes in which sulfur represses the synthesis of the more positive electron acceptors nitrate and fumarate (Lorenzen et al. 1993). The DMSO reductase from Escherichia coli (Weiner et al. 1988) has a broad substrate versatility, and is able to reduce a range of sulfoxides and A-oxides. Anaerobic sulfate reduction is not discussed here in detail. 

McCormick ML, GR Buettner, BE Britigan (1998) Endogenous superoxide dismutase levels regulate iron-dependent hydroxyl radical formation in Escherichia coli exposed to hydrogen peroxide. J Bacterial 180 622-625. 

Ornston LN, MK Ornston (1969) Regulation of glyoxylate metabolism in Escherichia coli K-12. J Bacterial 98 1098-1108. 

The biocatalytic approach is based on recombinant Escherichia coli growing in an aqueous mineral medium (Scheme 5.4). In Scheme 5.4, microbial growth is translated into a stoichiometric equation for biocatalyst synthesis. One needs to consider that biological safety regulations for recombinant class 1 organisms (no danger for humans and the environment) have to be followed with respect to biocatalyst handling. 

TNF is produced and secreted by activated cells within minutes following contact with LPS, reaching peak levels at 90-120 minutes after the admnistration of Escherichia coli endotoxin in human volunteers (M27). Van Deventer et al. (D15) could not detect serum TNF levels during experimental endotoxemia. Even during continuous intravenous administration of recombinant TNF (rTNF), serum TNF rapidly becomes undetectable (M27). It has been proposed that circulating soluble TNF receptors (sTNF-Rs) may be an important down-regulating mechanism (G10). 

Puskarova, A., Ferianc, P, Kormanec, J., Homerova, D., Farewell, A., and Nystrom, T., Regulation of yodA encoding a novel cadmium-induced protein in Escherichia coli, Microbiology, 148 (12), 3801-3811, 2002. 

Masse E. and Gottesman, S. (2002). A small RNA regulates the expression of genes involved in iron metabolism in Escherichia coli. Proc. Natl. Acad. Sci., 99, 4620 1625... 

Slonczewski JL et al. Add and base regulation in the proteome of Escherichia coli. Novartis Foundation Symp 1999 221 75-83. 

The nitrate (NOp content in crops is one of the most important indicators of farm production quality. Nitrate content in food is strictly regulated because of its toxicity, especially in young children. The actual toxin is not the nitrate ion itself but rather the nitrite ion (NOp, which is formed when nitrate is reduced by intestinal bacteria, notably Escherichia coli. In adults, nitrate is absorbed high in the digestive tract before reduction can take place. In infants, whose stomachs are less acidic, E. coli can colonize higher up the digestive tract and therefore reduce the NOJ to NCp before it is absorbed. 

Self, W. T., Grunden, A. M., Hasona, A., and Shanmugam, K. T. (1999). Transcriptional regulation of molybdoenzyme synthesis in Escherichia coli in response to molybdenum ModE-molybdate, a repressor of the modABCD (molybdate transport) operon is a secondary transcriptional activator for the hyc and nar operons. Microbiology 145, 41-55. 

---