ISOLEMENT ET CHARACTÉRISATION DE MUTANTS SENSIBLES OU RÉSISTANTS À L'OZONE CHEZESCHERICHIA COLIB

1982 ◽  
Vol 24 (5) ◽  
pp. 593-600 ◽  
Author(s):  
L. Poliquin ◽  
C. Hamelin ◽  
Y. S. Chung
Keyword(s):  
Escherichia Coli ◽  
Single Gene ◽  
Dna Lesions ◽  
The Other ◽  
Wild Type ◽  
Ozone Sensitivity ◽  
Other Hand ◽  
Radio Sensitivity ◽  
Escherichia Coli B

Escherichia coli B strains, either more sensitive or resistant to ozone than wild-type (OZsor OZr), were obtained after mutagenesis. OZsstrains carrying a mutation in ozrA or orzB, two genes located on both sides of malB, appeared as phenotypically different with regards to radio-sensitivity and cellular filamentation. OZrstrains, on the other hand, probably carry an allele of ozrA but were radioresistant and divided normally even with induction. A single gene (ozrA) thus seems to determine three levels of sensitivity to ozone, sensitivity to radiation and cellular filamentation in this organism. The possible involvement of a specific endonuclease in the repair of ozone-induced DNA lesions is considered.

scholarly journals Roles of RecJ, RecO, and RecR in RecET-Mediated Illegitimate Recombination in Escherichia coli

2002 ◽  
Vol 184 (17) ◽  
pp. 4715-4721 ◽  
Author(s):  
Kouya Shiraishi ◽  
Katsuhiro Hanada ◽  
Yoichiro Iwakura ◽  
Hideo Ikeda
Keyword(s):  
Escherichia Coli ◽  
Uv Irradiation ◽  
The Other ◽  
Illegitimate Recombination ◽  
Wild Type ◽  
Prophage Induction ◽  
Other Hand ◽  
In The Wild ◽  
Recombination Pathway

ABSTRACT We analyzed effects of overexpression of RecE and RecT on illegitimate recombination during prophage induction in Escherichia coli and found that frequencies of spontaneous and UV-induced illegitimate recombination are enhanced by coexpression of RecE and RecT in the wild type, but the enhanced recombination was reduced by recJ, recO, or recR mutation. The results indicated that RecET-mediated illegitimate recombination depends on the functions of RecJ, RecO, and RecR, suggesting that the RecE and RecJ exonucleases play different roles in this recombination pathway and that the RecO and RecR proteins also play important roles in the recombination. On the other hand, the frequency of the RecET-mediated illegitimate recombination was enhanced by a recQ mutation, implying that the RecQ protein plays a role in suppression of RecET-mediated illegitimate recombination. It was also found that RecET-mediated illegitimate recombination is independent of the RecA function with UV irradiation, but it is enhanced by the recA mutation without UV irradiation. Based on these results, we propose a model for the roles of RecJOR on RecET-mediated illegitimate recombination.

Homologous recombination involving a large heterology in Escherichia coli.

Genetics ◽  
1988 ◽  
Vol 119 (4) ◽  
pp. 759-769
Author(s):  
K Yamamoto ◽  
N Takahashi ◽  
H Yoshikura ◽  
I Kobayashi
Keyword(s):  
Escherichia Coli ◽  
Gene Conversion ◽  
Kanamycin Resistance ◽  
Coli Strain ◽  
The Other ◽  
Reca Gene ◽  
Inverted Repeats ◽  
Crossing Over ◽  
Wild Type ◽  
Parental Allele

Abstract Recombination between two different deletion alleles of a gene (neo) for neomycin and kanamycin resistance was studied in an Escherichia coli sbcA- recB-C- strain. The two homologous regions were in an inverted orientation on the same plasmid molecule. Kanamycin-resistant plasmids were selected and analyzed. The rate of recombination to form kanamycin-resistant plasmids was decreased by mutations in the recE, recF and recJ genes, but was not decreased by a mutation in the recA gene. It was found that these plasmids often possessed one wild-type kanamycin-resistant allele (neo+) while the other neo allele was still in its original (deletion) form. Among kanamycin-resistant plasmids with one wild-type and one parental allele it was often found that the region between the inverted repeats had been flipped (turned around) with respect to sites outside the inverted repeats. These results were interpreted as follows. Gene conversion, analogous to gene conversion in eukaryotic meiosis, is responsible for a unidirectional transfer of information from one neo deletion allele to the other. The flipping of the region between the inverted repeats is interpreted as analogous to the crossing over associated with gene conversion in eukaryotic meiosis. In contrast with a rec+ strain, these products cannot be explained by two rounds of reciprocal crossing over involving a dimeric form as an intermediate. In the accompanying paper we present evidence that gene conversion by double-strand gap repair takes place in the same E. coli strain.

Nutritional Requirement for 4-Aminobenzoate Caused by Mutation of Dihydropteroate Synthetase

1976 ◽  
Vol 31 (5-6) ◽  
pp. 285-287 ◽  
Author(s):  
Helmut Rappold ◽  
Adelbert Bacher
Keyword(s):  
Parent Strain ◽  
The Other ◽  
Synthetase Activity ◽  
Nutritional Requirement ◽  
Wild Type ◽  
Aerobacter Aerogenes ◽  
Low Level ◽  
Other Hand ◽  
High Concentrations

Abstract Aerobacter aerogenes mutant 62-1 AC requires high concentrations of 4-aminobenzoate for growth. The mutant accumulates N-glucosyl-4-aminobenzoate and has an intact 4-aminobenzoate synthetase (Bacher, Gilch, Rappold, and Lingens, Z. Naturforsch. 28c, 614 - 617 [1973]). On the other hand the ability of the mutant to synthesize dihydropteroate is markedly reduced. The dihydropteroate synthetase level of mutant 62-1 AC is 1% as compared to the parent strain. Spontaneous revertants of mutant 62-1 AC show wild type levels of dihydropteroate synthetase. We conclude that the requirement for 4-aminobenzoate in mutant 62-1 AC is due to poor utilization of 4-aminobenzoate as a consequence of the low level of dihydropteroate synthetase activity.

H-Ras Is Involved in the Inside-out Signaling Pathway of Interleukin-3–Induced Integrin Activation

Blood ◽  
1999 ◽  
Vol 93 (5) ◽  
pp. 1540-1548 ◽  
Author(s):  
Hirohiko Shibayama ◽  
Naoyuki Anzai ◽  
Stephen E. Braun ◽  
Seiji Fukuda ◽  
Charlie Mantel ◽  
...  
Keyword(s):  
Signaling Pathway ◽  
Dominant Negative ◽  
The Other ◽  
Wild Type ◽  
Integrin Activation ◽  
Mapk Kinase ◽  
Interleukin 3 ◽  
Other Hand ◽  
Inside Out ◽  
Constitutively Active

Abstract The proto-oncogene product, p21ras, has been implicated in the cellular mechanism of adhesion, although its precise role has been controversial. Numerous cytokines and growth-factors activate Ras, which is an important component of their growth-promoting signaling pathways. On the other hand, the role of Ras in cytokine-induced adhesion has not been elucidated. We therefore investigated the function of H-Ras in the inside-out signaling pathway of interleukin-3 (IL-3)–induced integrin activation in the murine Baf3 cell line after transfection of cells with either constitutively active, dominant-negative, or wild-type H-Ras cDNAs. Adhesion of Baf3 cells to fibronectin was induced by IL-3 in a dose-dependent manner via very late antigen-4 (VLA-4; 4β1 integrins) and VLA-5 (5β1 integrins) activation. On the other hand, IL-4 did not induce the adhesion of Baf3 cells to fibronectin, although IL-4 did stimulate the cell proliferation of Baf3 cells. Constitutively active H-Ras–transfected Baf3 cells adhered to fibronectin without IL-3 stimulation through VLA-4 and VLA-5, whereas dominant-negative H-Ras–transfected Baf3 cells showed significantly less adhesion induced by IL-3 compared with wild-type and constitutively active H-Ras–transfected Baf3 cells. Anti-β1 integrin antibody (clone; 9EG7), which is known to change integrin conformation and activate integrins, induced the adhesion of dominant-negative H-Ras–transfected Baf3 cells as much as the other types of H-Ras–transfected Baf3 cells. 8-Br-cAMP, Dibutyryl-cAMP, Ras-Raf-1 pathway inhibitors, and PD98059, a MAPK kinase inhibitor, suppressed proliferation and phosphorylation of MAPK detected by Western blotting with anti–phospho-MAPK antibody, but not adhesion of any type of H-Ras–transfected Baf3 cells, whereas U-73122, a phospholipase C (PLC) inhibitor, suppressed adhesion of these cells completely. These data indicate that H-Ras and PLC, but not Raf-1, MAPK kinase, or the MAPK pathway, are involved in the inside-out signaling pathway of IL-3–induced VLA-4 and VLA-5 activation in Baf3 cells.

scholarly journals Differential Biological and Adjuvant Activities of Cholera Toxin and Escherichia coli Heat-Labile Enterotoxin Hybrids

2001 ◽  
Vol 69 (3) ◽  
pp. 1528-1535 ◽  
Author(s):  
Christal C. Bowman ◽  
John D. Clements
Keyword(s):  
Escherichia Coli ◽  
Cyclic Amp ◽  
Cholera Toxin ◽  
The Other ◽  
Toxin Gene ◽  
Wild Type ◽  
B Subunit ◽  
Heat Labile ◽  
A Subunit ◽  
Ifn Γ

ABSTRACT Two bacterial products that have been demonstrated to function as mucosal adjuvants are cholera toxin (CT), produced by various strains of Vibrio cholerae, and the heat-labile enterotoxin (LT) produced by some enterotoxigenic strains of Escherichia coli. Although LT and CT have many features in common, they are clearly distinct molecules with biochemical and immunologic differences which make them unique. The goal of this study was to determine the basis for these biological differences by constructing and characterizing chimeric CT-LT molecules. Toxin gene fragments were subcloned to create two constructs, each expressing the enzymatically active A subunit of one toxin and the receptor binding B subunit of the other toxin. These hybrid toxins were purified, and the composition and assembly of CT A subunit (CT-A)-LT B subunit (LT-B) and LT A subunit (LT-A)-CT B subunit (CT-B) were confirmed. Hybrids were evaluated for enzymatic activity, as measured by the accumulation of cyclic AMP in Caco-2 cells, and the enterotoxicity of each toxin was assessed in a patent-mouse assay. The results demonstrated that LT-A–CT-B induces the accumulation of lower levels of cyclic AMP and has less enterotoxicity than either wild-type toxin or the other hybrid. Nonetheless, this hybrid retains adjuvant activity equivalent to or greater than that of either wild-type toxin or the other hybrid when used in conjunction with tetanus toxoid for intranasal immunization of BALB/c mice. Importantly, the ability of LT to induce a type 1 cytokine response was found to be a function of LT-A. Specifically, LT-A–CT-B was able to augment the levels of antigen-specific gamma interferon (IFN-γ) and interleukin 5 to levels comparable to those achieved with native LT, while CT-A–LT-B and native CT both produced lower levels of antigen-specific IFN-γ. Thus, these toxin hybrids possess unique biological characteristics and provide information about the basis for differences in the biological activities observed for CT and LT.

scholarly journals Effect of inhibition of DNA synthesis on mating inEscherichia coliK12

1965 ◽  
Vol 6 (3) ◽  
pp. 479-483 ◽  
Author(s):  
Susan Hollom ◽  
R. H. Pritchard
Keyword(s):  
Escherichia Coli ◽  
Amino Acid ◽  
Dna Replication ◽  
Dna Synthesis ◽  
Amino Acid Starvation ◽  
The Other ◽  
Thymine Starvation ◽  
Other Hand ◽  
Inhibition Of Dna Synthesis ◽  
Polynucleotide Chain

From studies involving inhibition of DNA synthesis in Hfr strains ofEscherichia coliK12, either by thymine starvation (Pritchard, 1963) or amino-acid starvation (Suit, Matney, Doudney & Billen, 1964), during mating withF−strains, it has been concluded that transfer of DNA from males to females can occur in the absence of DNA synthesis. This conclusion is at variance with the hypothesis (Jacob, Brenner & Cuzin, 1963) that the energy required for transfer is derived from the process of DNA replication. On the other hand, a second prediction from this hypothesis, that one polynucleotide chain of the DNA transferred during mating will have been synthesized during transfer, is strongly supported by recent experiments (Ptashne, 1965; Blinkova, Bresler & Lanzov, 1965; Gross & Caro, 1965).

scholarly journals Radiation-Induced Reversion of Transition Mutants

1964 ◽  
Vol 17 (4) ◽  
pp. 907 ◽  
Author(s):  
GW Grigg
Keyword(s):  
Escherichia Coli ◽  
Protein Synthesis ◽  
Base Pair ◽  
The Other ◽  
Wild Type ◽  
Lethal Effects ◽  
Reversion Frequency ◽  
X Irradiation ◽  
Radiation Induced ◽  
Adenine Thymine

X-irradiation increased the reversion frequency of two transition mutants of Escherichia coli, one of which (meth-) differed genetically from wild type by an adenine-thymine substitution of a guanine-cytosine base pair, the other (urg-2-) by a guanine-cytosine substitution of an adenine-thymine base pair. The lethal effects of the radiation were greatest when protein synthesis was prevented for a period immediately after irradiation. A period of 30 min at 37�0 was as effective as 22 hr. Irradiation of a saline suspension gave a lower survival of 0�2 times that of bacteria irradiated after being spread on minimal agar plates.

Abstract 16603: Appropriate Timing of Pacemaker Implantation in Patients With Wild-Type and Variant Amyloidogenic Transthyretin Cardiac Amyloidosis

Circulation ◽  
2020 ◽  
Vol 142 (Suppl_3) ◽  
Author(s):  
Yusei Kawahara ◽  
Miwa Ito ◽  
Tadashi Hoshiyama ◽  
Hisanori Kanazawa ◽  
Kenichi Tsujita
Keyword(s):  
Cardiac Amyloidosis ◽  
Pacemaker Implantation ◽  
The Other ◽  
Cardiac Conduction ◽  
Wild Type ◽  
Conduction Disorders ◽  
Other Hand ◽  
Conduction Disorder ◽  
Second Degree

Background and Objectives: It has been shown that cardiac conduction disorders can be seen in patients with wild-type amyloidogenic transthyretin (ATTRwt) and variant ATTR (ATTRv) cardiac amyloidosis. However, its appropriate timing of pacemaker implantation has not been clarified yet. Methods and Results: The consecutive 100 patients with ATTRwt cardiac amyloidosis who diagnosed by myocardium biopsy and/or technetium-99m-pyrophosphate scintigraphy and 62 patients with ATTRv cardiac amyloidosis who diagnosed by means of genetic screening were included in this study. In patients with ATTRwt cardiac amyloidosis, 21 patients have normal conduction at the time of diagnosis. However, conduction disorder had seen in only 5 patient (first degree atrioventricular block (AVB); 4 patients, complete AVB; 1 patients) and only one patient underwent cardiac implantable electric device (CIED) implantation during follow-up period. On the other hand, in patients with ATTRv cardiac amyloidosis, 36 patients have normal conduction at the time of diagnosis. However, conduction disorder had seen in 13 patient (first degree AVB; 8 patients, second degree AVB; 3 patients, trifascicular block; 1 patients, complete AVB; 1 patients) (5/21 vs 13/36, p=0.335) and 6 patients underwent CIED implantation during follow-up period (1/21 vs 6/36, p=0.186). Furthermore, in ATTRwt cardiac amyloidosis, 10 patients (first degree AVB; 2 patients, second degree AVB; 1 patient, trifascicular block; 7 patients) had underwent CIED implantation because of cardiac conduction disorders and/or prevention of sudden cardiac death. However, only 4 patients with trifascicular block progressed to complete AVB.On the other hand, In ATTRv cardiac amyloidosis, 14 patients (first degree AVB; 2 patients, second degree AVB; 4 patient, trifascicular block; 8 patients) had underwent CIED implantation for same reason. However, only 3 patients with trifascicular block progressed to complete AVB. Conclusions: Patients with ATTRv cardiac amyloidosis were more likely to progress conduction disorders than those with ATTRwt cardiac amyloidosis. However, prophylactic pacemaker implantation might had not need in both ATTRwt and ATTRv patients with first or second degree AVB.

Gut Flora in Autistic Children as Biomarker for Autism in Thi-Qar Province/Iraq

2020 ◽  
pp. 73-79
Keyword(s):  
Escherichia Coli ◽  
Enterococcus Faecalis ◽  
The Other ◽  
Bacterial Isolates ◽  
Autistic Children ◽  
Gram Positive ◽  
Gram Negative ◽  
Other Hand ◽  
Significant Difference ◽  
Gram Positive Cocci

This is the first study that investigated the microbial factor as biomarker in autistic children and discuss roles of this factor in the pathogenesis of autism. The participants in current study were 145 persons, only 50 sample of stool could collected (35 autistic children and 15 healthy children). Autistic children were attended to autism unit at Disabled Hospital in Thi-Qar province, Iraq during the period from January to November 2016. The results showed males (81%) more than female (19%) with ratio 4:1 and also results explain the age group of 3-5 years recorded the highest percentage (41.05%). Distribution of autistic children according to sibling showed six were brotherly with occurrence rate 6.3%. Stool samples were subjected to examination and culture. The total aerobic count of isolated bacteria was 140 isolates. Gram-negative isolates were identified by API Enterobacteriaceae system. The results were Escherichia coli, Enterobacter cloacae, Klebsiella pneumonia, Pseudomonas aeruginosa and Proteus mirabilis with percentage 38.5%, 19.23%, 11.53%,7.69%, and 3.84% respectively. On the other hand, gram positive cocci isolates included Enterococcus faecalis, Staphylococcus aureus and Staph. epidermidis with percentage 11.53%, 4.80% and 2.88% respectively. A significant difference (P≤0.05) was recorded between bacterial isolates. Quantity and quality of isolated bacteria (colony/g *104) were done. E.coli isolates were the highest count with 261*104 colony/g while, Staphylococci epidermidis were recorded the worse colony count with 30*104 colony/g. The quality results showed Escherichia coli the most common gram negative bacterial isolates (38.46%). On the other hand, the highest gram positive cocci isolates were included Enterococcus faecalis (11.53%), with significant difference (P≤0.05) between bacterial isolates. The ability of bacterial isolates to produce histidine decarboxylase was examined on Niven medium. The positive result include colonies with purple halo around them. Only 10 isolates (25%) from all isolates were produce histidine belong to E.coli. On other hand, result of parasite examination explain no parasite in all samples. From this study can conclusion the altered gut microflora may play an essential role in the pathogenesis of autism. Despite the accurate evidence, this etiological heterogeneity is still not recognized by autism researchers, and most studies fail to take it into account.

Suppression of dual-effect mutants of the L-ribulokinase structural gene of Escherichia coli B/r

1971 ◽  
Vol 17 (8) ◽  
pp. 1105-1114
Author(s):  
Morad Abou-Sabe
Keyword(s):  
Enzyme Level ◽  
The Other ◽  
Wild Type ◽  
Dual Effect ◽  
Wild Type Level ◽  
Suppressor Mutations ◽  
Extragenic Suppressors ◽  
Escherichia Coli B ◽  
Distinct Increase ◽  
Arabinose Isomerase

A number of extragenic suppressors for two-dual effect, polarity, and hyperinducible L-ribulokinaseless mutants were isolated and enzymatically characterized. The effect of the suppressors on L-arabinose isomerase and L-ribulokinase enzyme activities was tested using a variety of arar suppressor-carrying strains. The effect of these suppressor mutations on T4 amber and ocher mutants was also studied. Results show that low-dual-effect, i.e. polarity, araB− suppressor-carrying strains invariably have a distinct increase in the L-arabinose isomerase enzyme level, above the wild-type level, irrespective of the restoration of the L-ribulokinase enzyme activity. High-dual-effect, hyperinducible, suppressed mutants, on the other hand, were not significantly altered in their L-arabinose isomerase enzyme level. It is also found that four different T4 amber mutants were suppressible by all tested suppressor-carrying strains, while T4 ocher mutants were not. It is concluded that the suppressor mutations studied are amber-like suppressors acting at the translation level, and that both polarity mutant araB68 and hyperinducible mutant araBA87 are nonsense mutants. The phenomenon of hyperinducibility is also discussed.

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