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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: It is shown that the toxin of the prokaryote Bordetella pertussis is synthesized in a large precursor form composed of 1706 amino acids, and that the calmodulin‐stimulated catalytic activity resides in the amino‐terminal 450 amino acids of the adenylate cyclase.
Abstract: The adenylate cyclase toxin of the prokaryote Bordetella pertussis is stimulated by the eukaryotic regulatory protein, calmodulin. A general strategy, using the adenylate-cyclase-calmodulin interaction as a tool, has permitted cloning and expression of the toxin in Escherichia coli in the absence of any B. pertussis trans-activating factor. We show that the protein is synthesized in a large precursor form composed of 1706 amino acids. The calmodulin-stimulated catalytic activity resides in the amino-terminal 450 amino acids of the adenylate cyclase. The enzyme expressed in E. coli is recognized in Western blots by antibodies directed against purified B. pertussis adenylate cyclase, and its activity is inhibited by these antibodies.

308 citations

Journal ArticleDOI
TL;DR: The results demonstrate that antimicrobial resistance epidemiology differs significantly between pathogenic and commensal E. coli isolates and may have important implications with regards to the spread and persistence of resistance and virulence genes in bacterial populations and to the prudent use of antimicrobial agents.
Abstract: A total of 318 Escherichia coli isolates obtained from diarrheic and healthy pigs in Ontario from 2001 to 2003 were examined for their susceptibility to 19 antimicrobial agents. They were tested by PCR for the presence of resistance genes for tetracycline, streptomycin, sulfonamides, and apramycin and of 12 common virulence genes of porcine E. coli. Antimicrobial resistance frequency among E. coli isolates from swine in Ontario was moderate in comparison with other countries and was higher in isolates from pigs with diarrhea than in isolates from healthy finisher pigs. Resistance profiles suggest that cephamycinases may be produced by ≥8% of enterotoxigenic E. coli (ETEC). Resistance to quinolones was detected only in enterotoxigenic E. coli (≤3%). The presence of sul3 was demonstrated for the first time in Canada in porcine E. coli isolates. Associations were observed among tetA, sul1, aadA, and aac(3)IV and among tetB, sul2, and strA/strB, with a strong negative association between tetA and tetB. The paa and sepA genes were detected in 92% of porcine ETEC, and strong statistical associations due to colocation on a large plasmid were observed between tetA, estA, paa, and sepA. Due at least in part to gene linkages, the distribution of resistance genes was very different between ETEC isolates and other porcine E. coli isolates. This demonstrates that antimicrobial resistance epidemiology differs significantly between pathogenic and commensal E. coli isolates. These results may have important implications with regards to the spread and persistence of resistance and virulence genes in bacterial populations and to the prudent use of antimicrobial agents.

307 citations

Journal ArticleDOI
TL;DR: A pair of low copy number plasmids which contain a 580 bp BstVl fragment that carries the lac promoter/operator, multiple cloning sites and lacZ fragment of pUC19 cloned in place of the poly linker region in pGB2 are constructed.
Abstract: We have constructed pCL1920 and pCL1921, a pair of low copy number plasmids which contain a 580 bp BstVl fragment that carries the lac promoter/operator, multiple cloning sites and lacZ fragment of pUC19 (1) cloned in place of the poly linker region in pGB2 (2), a pSClOl derived plasmid which confers spectinomycin (50 jtg/ml) and streptomycin (100 jig/ml) resistance in Escherichia coli. All multiple cloning sites indicated are unique except for an additional EcoRI site as shown in the figure. pCL1920 and pCL1921 contain the BstVl fragment in opposite orientations with respect to the pGB2 sequences. In the absence of inducer the pCL1920/21 vectors do not produce detectable levels of/3-galactosidase in JM105 (lacP lacZAM\\5) (1) cells (less than 2 Miller units) (3). In the presence of 2 mM IPTG (isopropyl-j3-D-thiogalactopyranoside) the /3galactosidase levels of the pCL1920/21 [JM105] transformants rose to 11 units, while the pUC19 [JM105] transformants produced 470 units; a 43 fold increase. These results are consistent with the expected 40 fold difference in plasmid copy number between pCL 1920/21 (5 copies per cell) compared to that of the pUC vectors (200 copies per cell). Thus the pCL1920 and pCL1921 vectors allow

307 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