Mesosomes in Escherichia coli

When Escherichia coli was grown in a synthetic medium and fixed with osmium, sections of the cells revealed clearly defined mesosomes. These mesosomes appeared to develop, in dividing cells, as coiled infoldings of the cytoplasmic membrane. Mature mesosomes formed a link between the cytoplasmic membrane and the nucleus of the cell. The arrangement of the mesosomes in dividing cells led to the hypothesis that division of the nucleus in these cells is accomplished by two separate polar mesosomes. One mesosome is derived from the parent cell and is present at one pole of the daughter cell. The other is freshly synthesized at or near the newly forming pole of the daughter cell. While the old mesosome remains attached to the chromosome received from the parent cell, the newly synthesized mesosome becomes attached to and initiates replication of the new chromosome. As the cell grows and elongates, the two mesosomes, attached to their respective chromosomes move apart, thus effecting nuclear division.     

Pathogenic Escherichia coli

Few microorganisms are as versatile as Escherichia coli. An important member of the normal intestinal microflora of humans and other mammals, E. coli has also been widely exploited as a cloning host in recombinant DNA technology. But E. coli is more than just a laboratory workhorse or harmless intestinal inhabitant; it can also be a highly versatile, and frequently deadly, pathogen. Several different E. coli strains cause diverse intestinal and extraintestinal diseases by means of virulence factors that affect a wide range of cellular processes.     

Escherichia coli neuraminidase

The intracellular form of neuraminidase has been detected in E. coli and Proteus vulgaris. Neuraminidase has been isolated from E. coli HB 101 cells and purified 118-fold. Some physico-chemical properties of this enzyme have been studied.     

Thymineless Mutagenesis in Escherichia coli

To clarify the relationship between thymineless death and thymineless mutagenesis, the induction of arginine revertants of Escherichia coli TAU-bar by thymine starvation was examined in physiological terms. Induced revertants were detectable both on minimal medium lacking arginine and minimal medium supplemented with 1 mug of arginine per ml. Substantial thymineless mutagenesis occurred during the period before the onset of thymineless death. Mutagenesis and loss of viability were observed upon incubation in medium lacking thymine and arginine, and both were inhibited upon incubation in medium lacking thymine and uracil. Mutagenesis also occurred during thymine starvation at 25 C, where there was relatively little loss of viability. At 37 C thymineless mutagenesis did not require complete thymine starvation, and the induction of revertants appeared to be initiated at the same suboptimal thymine concentration at which lethality was first detectable. Mutagenesis was found not to occur preferentially at the growing point of deoxyribonucleic acid replication. These results suggest that thymineless mutagenesis does not involve simply errors in base pairing due to the absence of thymine. The data also suggest that the induction of mutations and thymineless death are due to the same primary event but that mutagenesis is the more sensitive response.     

Selenium metabolism in Escherichia coli

Escherichia coli will reduce selenite (SeO 3 2- ) andselenate (SeO 4 2- ) to elemental selenium Se 0 . Seleniumwill also become incorporated intoproteins as part of the amino acids selenocysteine or selenomethionine.The reaction of selenitewith glutathione produces selenodiglutathione (GS-Se-GS). Selenodiglutathioneand itssubsequent reduction to glutathioselenol (GS-SeH) are likely the key intermediatesin the possiblemetabolic fates of selenium. This review presents the possible pathwaysinvolving selenium in E. coli. Identification of intermediates and potentialprocesses from uptake of the toxic oxyanions through to theirdetoxification will assist us inunderstanding the complexities of metalloid oxyanion metabolism in thesebacteria.     

Gluconate Metabolism in Escherichia coli

On the basis of information available in the literature, gluconate dissimilation in Escherichia coli is thought to occur via the hexose monophosphate pathway. Evidence is presented in this study that gluconate is catabolized in this organism via an inducible Entner-Doudoroff pathway. This evidence is based on chromatographic examination of end products produced from (14)C-labeled gluconate or glucose, distribution of (14)C in the carbon atoms of pyruvate formed from specifically labeled (14)C-glucose and (14)C-gluconate, and the ability of cell-free extracts to produce pyruvate from 6-phosphogluconate. Degradation of gluconate by an Entner-Doudoroff pathway occurred simultaneously with a glycolytic cleavage of glucose. A relationship between gluconate-induced, Entner-Doudoroff pathway activity and catabolism of glucose in Escherichia coli and other bacterial species is discussed.     

Protoplast Formation in Escherichia coli

A procedure for protoplast formation in Escherichia coli is described. Removal of the cell wall was confirmed by examination of cells in thin-section preparations.     

Succinate production in Escherichia coli

Succinate has been recognized as an important platform chemical that can be produced from biomass. While a number of organisms are capable of succinate production naturally, this review focuses on the engineering of Escherichia coli for the production of four-carbon dicarboxylic acid. Important features of a succinate production system are to achieve an optimal balance of reducing equivalents generated by consumption of the feedstock, while maximizing the amount of carbon channeled into the product. Aerobic and anaerobic production strains have been developed and applied to production from glucose and other abundant carbon sources. Metabolic engineering methods and strain evolution have been used and supplemented by the recent application of systems biology and in silico modeling tools to construct optimal production strains. The metabolic capacity of the production strain, the requirement for efficient recovery of succinate, and the reliability of the performance under scaleup are important in the overall process. The costs of the overall biorefinery-compatible process will determine the economic commercialization of succinate and its impact in larger chemical markets.