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.

Characteristics of Some Multiply Recombination-Deficient Strains of Escherichia coli

Abstract: Strains of Escherichia coli have been made carrying lesions in more than one gene determining recombination. The following genotypes were constructed and verified: recC22 recB21 recA(+), recC22 recB21 recA13, recC22 recB(+)recA13, and recC(+)recB21 recA13. All multiple rec(-) strains carrying recA13 were similar to AB2463, which carries recA13 alone, in their UV sensitivities, recombination deficiencies, and inabilities to induce lambda phage in a lysogen. However, whereas AB2463 shows a high rate of ultraviolet (UV)-induced deoxyribonucleic acid (DNA) breakdown, the multiple rec(-) strains showed the low level characteristic of strains carrying recC22 or recB21 alone. The strain carrying both recC22 and recB21 was similar in all properties to the single mutants, suggesting that both gene products act in the same part of the recombination and UV repair pathways. It is concluded that in a Rec(+) strain, the recA(+) product acts to inhibit DNA breakdown determined by the recC(+) and recB(+) products.

General transduction in Rhizobium meliloti.

Abstract: General transduction by phage phi M12 in Rhizobium meliloti SU47 and its derivatives is described. Cotransduction and selection for Tn5 insertions which are closely linked to specific loci were demonstrated. A derivative of SU47 carrying the recA::Tn5 allele of R. meliloti 102F34 could be transduced for plasmid R68.45 but not for chromosomally located alleles. Phage phi M12 is morphologically similar to Escherichia coli phage T4, and restriction endonuclease analysis indicated that the phage DNA was ca. 160 kilobases in size. Images

Evolutionary conservation of components of the protein translocation complex

Abstract: PROTEIN translocation into the mammalian endoplasmic reticulum requires the Sec61p complex, which consists of three membrane proteins1. The α-subunit, the homologue of Sec61p of yeast2–4, shows some similarity to SecYp5, a key component of the protein export apparatus of bacteria6,7. In Escherichia coli, SecYp is also associated with two other proteins (SecEp and band-1 protein)8,9. We have now determined the sequences of the β- and γ-subunits of the mammalian Sec61p complex. Sec61-γ is homologous to SSSlp, a suppressor of sec61 mutants in Saccharomyces cerevisiae, and can functionally replace it in yeast cells. Moreover, Sec61-γ and SSSlp are structurally related to SecEp of E. coli and to putative homologues in various other bacteria. At least two sub-units of the Sec61/SecYp complex therefore seem to be key components of the protein translocation apparatus in all classes of organisms.

Is acetyl phosphate a global signal in Escherichia coli

Abstract: In this article we discuss recent evidence indicating that acetyl phosphate may be a global signal in Escherichia coli and related bacteria. We shall start by reviewing the evidence that acetyl phosphate is involved in signal transduction by a family of related phosphorylation-dependent switches known as the two-component systems. We shall also review the data indicating the mechanism by which acetyl phosphate affects the function of these switches. Finally, we shall review the factors affecting the intracellular concentration of acetyl phosphate in an attempt to deduce the significance of the signal provided by acetyl phosphate. We conclude by offering two suggestions for the role of acetyl phosphate as a potential global signal.

Mutants of Escherichia coli K12 unable to use fumarate as an anaerobic electron acceptor.

Abstract: Summary: Mutants of Escherichia coli K12 strain WGAS-GF+/LF+ were selected for their inability to use fumarate as terminal electron acceptor for supporting growth on glycerol or lactate in an atmosphere of H2 plus 5% CO2. Eighty-three mutants were grouped into seven different categories according to their ability to grow on different media and their ability to produce gas during glucose fermentation. Enzymological and genetic studies indicated that the major class (type I), representing nearly 70% of the isolates, lacked fumarate reductase and corresponded to the frdA mutants studied previously (Spencer & Guest, 1973, 1974). Members of a second class (type II) were phenotypically similar to men mutants, blocked in menaquinone biosynthesis. They differed from menA mutants in having lesions in the 44 to 51 min region of the chromosome rather than at 87 min. It was concluded that fumarate reductase and menaquinone are essential for anaerobic growth when fumarate serves as electron acceptor but not when nitrate performs this function. Fumarate reductase and menaquinone are also essential for H2-dependent growth on fumarate. Type III mutants, originally frdB, were designated fnr because they were defective in fumarate and nitrate reduction and impaired in their ability to produce gas. The fnr gene was located at 28·5 min by its cotransducibility with pyrF (5·7 to 9·2%) and trpA (2·7 to 5·7%) and the gene order fnr-qmeA-pyrF-trpA was established. It was not possible to assign specific metabolic lesions to the fnr mutants nor to the remaining classes, which all exhibited pleiotropic phenotypes. Nevertheless, the results demonstrate that functional or organizational relationships exist between the fumarate reductase system, nitrate reduction and hydrogen production.