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.

Probiotic Bifidobacteria Protect Mice from Lethal Infection with Shiga Toxin-Producing Escherichia coli O157:H7

Abstract: The anti-infectious activity of probiotic Bifidobacteria against Shiga toxin-producing Escherichia coli (STEC) O157:H7 was examined in a fatal mouse STEC infection model. Stable colonization of the murine intestines was achieved by the oral administration of Bifidobacterium breve strain Yakult (naturally resistant to streptomycin sulfate) as long as the mice were treated with streptomycin in their drinking water (5 mg/ml). The pathogenicity of STEC infection, characterized by marked body weight loss and subsequent death, observed in the infected controls was dramatically inhibited in the B. breve-colonized group. Moreover, Stx production by STEC cells in the intestine was almost completely inhibited in the B. breve-colonized group. A comparison of anti-STEC activity among several Bifidobacterium strains with natural resistance to streptomycin revealed that strains such as Bifidobacterium bifidum ATCC 15696 and Bifidobacterium catenulatum ATCC 27539T did not confer an anti-infectious activity, despite achieving high population levels similar to those of effective strains, such as B. breve strain Yakult and Bifidobacterium pseudocatenulatum DSM 20439. The effective strains produced a high concentration of acetic acid (56 mM) and lowered the pH of the intestine (to pH 6.75) compared to the infected control group (acetic acid concentration, 28 mM; pH, 7.15); these effects were thought to be related to the anti-infectious activity of these strains because the combination of a high concentration of acetic acid and a low pH was found to inhibit Stx production during STEC growth in vitro.

System for High-Level Production in Escherichia coli and Rapid Purification of Recombinant Proteins: Application to Epitope Mapping, Preparation of Antibodies, and Structure—Function Analysis

Abstract: Publisher Summary This chapter presents an application of the system for high-level production in Escherichia coli and rapid purification of recombinant proteins The advent of gene cloning, the engineering of vectors for efficient expression, and the application of fast and high-flux methods for protein purification made available many recombinant proteins of biological interest This represented a breakthrough for the structure–function analysis of bioactive proteins and cell receptors and facilitated X-ray crystallographic studies for definition of the three-dimensional structures of these proteins The E coli expression system allows the high-level production of recombinant proteins in authentic form, as fusion proteins with the [His] 6 affinity tail and with mouse DHFR and the [His] 6 tail Because of the presence of the affinity tail, proteins that are produced in a soluble form or can be solubilized with GuHCl or urea can be purified almost to homogeneity in one step by nickel chelate affinity chromatography The purified recombinant proteins simplify the production of monoclonal and polyclonal antibodies directed against defined regions of the native proteins

Nucleotide sequence of the Escherichia coli cad operon: a system for neutralization of low extracellular pH.

Abstract: Lysine decarboxylase of Escherichia coli has been the subject of enzymological studies, and the gene encoding lysine decarboxylase (cadA) and a regulatory gene (cadR) have been mapped. This enzyme is induced at low pH in the presence of lysine and achieves maximal level under anaerobic conditions. The induction of lysine decarboxylase increases the pH of the extracellular medium and provides a distinctive marker in tests of clinical strains. We report the sequence of the cad operon encoding lysine decarboxylase, a protein of 715 amino acids, and another protein, CadB, of 444 amino acids. The amino acid sequence of lysine decarboxylase showed high homology to that of the lysine decarboxylase of Hafnia alvei with less homology to the sequence of speC, which encodes the biosynthetic ornithine decarboxylase of E. coli. The cadA and cadB genes were separately cloned and placed under the control of lac and tac promoters, respectively, to facilitate independent study of their physiological effects. The cadB gene product had a mobility characteristic of a smaller protein on protein gels, analogous to that found for some other membrane proteins. The CadB sequence showed homology to that of ArcD of Pseudomonas aeruginosa, encoding an arginine/ornithine antiporter. Excretion studies of various strains, the coinduction of cadB and cadA, and the attractive physiological role for an antiport system led to a model for the coupled action of cadA and cadB in uptake of lysine, the reduction of H+ concentration, and excretion of cadaverine.

Genetic Studies of Lysogenicity in Escherichia Coli.

Abstract: ECENT research on Escherichia coli phages has outlined the biology of R viruses that promptly lyse their bacterial hosts (DELBRUCK 1950). In addition to the progressive parasitic relationship that these studies have analyzed, many phage-bacterium complexes persist in a more enduring symbiosis, lysogenicity. The experiments to be described in this paper were designed to probe two related questions: how is the virus of a lysogenic bacterium transmitted in vegetative and sexual reproduction? and how is a symbiotic complex established following infection by the virus, as an alternative to the parasitization and lysis of the host bacterium ? Complementary problems, especially concerning the growth and release of virus in lysogenic bacteria have received more emphasis from other workers (BERTANI 1951 ; LWOFF and GUTMANN 1950; WEIGLE and DELBRUCK 1951). Our interest in lysogenicity was provoked by the discovery that E. coli strain K-12 was lysogenic. On two occasions, mixtures of certain mutant stocks appeared to be contaminated with bacteriophage. The plaques were unusual in showing turbid centers, suggesting those figured by BURNET and LUSH (1936). I t soon became apparent that practically all K-12 cultures carried this latent phage. The novelty consisted of two exceptional mutant substrains, W-435 and W-518 which were sensitive to the phage, now referred to as A. These two strains had been maintained in our stocks as nonfermenting mutants for lactose (Lacs-) and galactose ( GaZ4-Lacl-), respectively, isolated from ultraviolet-treated suspensions. Both cultures are derived from 58-161, a methionine-requiring auxotroph previously used in many recombination experiments ( TATUM 1945 ; TATUM and LEDERBERG 1947). The lysogenicity of strain K-12 had remained unsuspected despite its maintenance for over 25 years and close study as the subject of mutation and recombination experiments since 1944. However, the only objective criterion of a lysogenic symbiosis is the lysis of another sensitive strain that functions as an indicator. Thus, in the absence of an appropriate conjunction of strains the virus carried by the I<-12 subline would remain undetected. Because of the low frequency of sensitive strains, such Clpportunities are rare. The development of crossing techniques in strain K-12 has allowed the virus to be studied as a genetic factor. Intercrosses among strains differing with respect to h and the development of lysogenic from sensitive strains are the main subjects of this report. .