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Escherichia coli

About: Escherichia coli is a research topic. Over the lifetime, 59041 publications have been published within this topic receiving 2050337 citations. The topic is also known as: E. coli & E coli jdj.


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Journal ArticleDOI
TL;DR: The methylase responsible for resistance to macrolides, lincomycin, and streptogramin B-related antibiotics in Staphylococcus aureus also acts at this site.

243 citations

Journal ArticleDOI
TL;DR: This is the first report of a membrane phospholipid desaturase in a nonphotosynthetic organism and the first direct evidence for cold induction of a desaturases.
Abstract: Bacillus subtilis grown at 37 degrees C synthesizes saturated fatty acids with only traces of unsaturated fatty acids (UFAs). However, when cultures growing at 37 degrees C are transferred to 20 degrees C, UFA synthesis is induced. We report the identification and characterization of the gene encoding the fatty acid desaturase of B. subtilis. This gene, called des, was isolated by complementation of Escherichia coli strains with mutations in either of two different genes of UFA synthesis. The des gene encodes a polypeptide of 352 amino acid residues containing the three conserved histidine cluster motifs and two putative membrane-spanning domains characteristic of the membrane-bound desaturases of plants and cyanobacteria. Expression of the des gene in E. coli resulted in desaturation of palmitic acid moieties of the membrane phospholipids to give the novel mono-UFA cis-5-hexadecenoic acid, indicating that the B. subtilis des gene product is a delta5 acyl-lipid desaturase. The des gene was disrupted, and the resulting null mutant strains were unable to synthesize UFAs upon a shift to low growth temperatures. The des null mutant strain grew as well as its congenic parent at 20 or 37 degrees C but showed severely reduced survival during stationary phase. Analysis of operon fusions in which the des promoter directed the synthesis of a lacZ reporter gene showed that des expression is repressed at 37 degrees C, but a shift of cultures from 37 to 20 degrees C resulted in a 10- to 15-fold increase in transcription. This is the first report of a membrane phospholipid desaturase in a nonphotosynthetic organism and the first direct evidence for cold induction of a desaturase.

243 citations

Journal ArticleDOI
TL;DR: A broad array of virulence genes associated with PWD in pigs are suggested, including non-fimbrial adhesin paa, which was found present in over half of the K88+ isolates and most of these isolates carried multiple toxin genes.

243 citations

Journal ArticleDOI
TL;DR: A comparative analysis of all published complete genomes indicated that the putative orthologs of the unannotated ychB gene of Escherichia coli follow the distribution of the dxs, dxr, and ygbP genes, thus suggesting that the hypothetical YchB protein also is involved in that pathway of terpenoid biosynthesis.
Abstract: A comparative analysis of all published complete genomes indicated that the putative orthologs of the unannotated ychB gene of Escherichia coli follow the distribution of the dxs, dxr, and ygbP genes, which have been shown to specify enzymes of the deoxyxylulose phosphate pathway of terpenoid biosynthesis, thus suggesting that the hypothetical YchB protein also is involved in that pathway. To test this hypothesis, the E. coli ychB gene was expressed in a homologous host. The recombinant protein was purified to homogeneity and was shown to phosphorylate 4-diphosphocytidyl-2C-methyl-d-erythritol in an ATP-dependent reaction. The reaction product was identified as 4-diphosphocytidyl-2C-methyl-d-erythritol 2-phosphate by NMR experiments with various 13C-labeled substrate samples. A 14C-labeled specimen of this compound was converted efficiently into carotenoids by isolated chromoplasts of Capsicum annuum. The sequence of E. coli YchB protein is similar to that of the protein predicted by the tomato cDNA pTOM41 (30% identity), which had been implicated in the conversion of chloroplasts to chromoplasts.

243 citations

Journal ArticleDOI
TL;DR: This finding indicates that reversible methylation acts as a control mechanism and that both a methyltransferase and a protein methylesterase are instrumental in bacterial sensing.
Abstract: A protein methylesterase has been identified in soluble extracts of Salmonella typhimurium and Escherichia coli. This enzyme catalyzes the hydrolysis of gamma-glutamyl methyl ester residues from membrane-bound 60,000-molecular weight proteins that are essential for chemotaxis. Analyses of methylesterase activity in a variety of chemotactically defective strains suggest that the methylesterase is a product of the cheX gene in Salmonella and the cheB gene in E. coli. In addition, the cheT gene product in S. typhimurium seems to play a role in expression of methylesterase activity. Mutant strains lacking the protein methylesterase tumble incessantly in the absence of attractant gradients. This behavior is the converse of that shown by mutant strains defective in methyltransferase activity, which swim smoothly in the absence of repellent gradients. This finding indicates that reversible methylation acts as a control mechanism and that both a methyltransferase and a protein methylesterase are instrumental in bacterial sensing.

242 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20242
20232,609
20225,796
20211,236
20201,337
20191,412