Assessment of the toxic and protective effects of initiators and inhibitors of free radical reactions using a wild-type strain ofEscherichia coli and a strain deficient for superoxide dismutase

1996 ◽  
Vol 121 (1) ◽  
pp. 67-71
Author(s):  
M. V. Bilenko ◽  
V. G. Ladygina ◽  
I. A. Tarakanova
Keyword(s):  
Superoxide Dismutase ◽  
Free Radical ◽  
Type Strain ◽  
Wild Type Strain ◽  
Ofescherichia Coli ◽  
Radical Reactions ◽  
Protective Effects ◽  
Wild Type ◽  
Free Radical Reactions ◽  
Strain Ofescherichia Coli

scholarly journals Copper-Modulated Gene Expression and Senescence in the Filamentous Fungus Podospora anserina

2001 ◽  
Vol 21 (2) ◽  
pp. 390-399 ◽  
Author(s):  
Corina Borghouts ◽  
Alexandra Werner ◽  
Thomas Elthon ◽  
Heinz D. Osiewacz
Keyword(s):  
Superoxide Dismutase ◽  
Transcription Factor ◽  
Type Strain ◽  
Wild Type Strain ◽  
Podospora Anserina ◽  
Wild Type ◽  
Transcript Levels ◽  
Important Impact ◽  
Cellular Copper ◽  
Copper Depletion

ABSTRACT We have previously shown that the control of cellular copper homeostasis by the copper-modulated transcription factor GRISEA has an important impact on the phenotype and lifespan of Podospora anserina. Here we demonstrate that copper depletion leads to the induction of an alternative respiratory pathway and to an increase in lifespan. This response compensates mitochondrial dysfunctions via the expression of PaAox, a nuclear gene coding for an alternative oxidase. It resembles the retrograde response inSaccharomyces cerevisiae. In P. anserina, this pathway appears to be induced by specific impairments of the copper-dependent cytochrome c oxidase. It is not induced as the result of a general decline of mitochondrial functions during senescence. We cloned and characterized PaAox. Transcript levels are decreased when cellular copper, superoxide, and hydrogen peroxide levels are raised. Copper also controls transcript levels ofPaSod2, the gene encoding the mitochondrial manganese superoxide dismutase (PaSOD2). PaSod2 is a target of transcription factor GRISEA. During the senescence of wild-type strain s, the activity of PaSOD2 decreases, whereas the activity of the cytoplasmic copper/zinc superoxide dismutase (PaSOD1) increases. Collectively, the data explain the postponed senescence of mutant grisea as a defined consequence of copper depletion, ultimately leading to a reduction of oxidative stress. Moreover, they suggest that during senescence of the wild-type strain, copper is released from mitochondria. The involved mechanism is unknown. However, it is striking that the permeability of mitochondrial membranes in animal systems changes during apoptosis and that mitochondrial proteins with an important impact on this type of cellular death are released.

Evaluation of a new copper(II)–curcumin complex as superoxide dismutase mimic and its free radical reactions

2005 ◽  
Vol 39 (6) ◽  
pp. 811-822 ◽  
Author(s):  
Atanu Barik ◽  
Beena Mishra ◽  
Liang Shen ◽  
Hari Mohan ◽  
R.M. Kadam ◽  
...  
Keyword(s):  
Superoxide Dismutase ◽  
Free Radical ◽  
Radical Reactions ◽  
Free Radical Reactions ◽  
Superoxide Dismutase Mimic

scholarly journals Increased Expression of Periplasmic Cu,Zn Superoxide Dismutase Enhances Survival of Escherichia coli Invasive Strains within Nonphagocytic Cells

2000 ◽  
Vol 68 (1) ◽  
pp. 30-37 ◽  
Author(s):  
Andrea Battistoni ◽  
Francesca Pacello ◽  
Silvia Folcarelli ◽  
Maria Ajello ◽  
Giovanna Donnarumma ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Superoxide Dismutase ◽  
Epithelial Cells ◽  
Type Strain ◽  
Wild Type Strain ◽  
Yersinia Pseudotuberculosis ◽  
Host Cells ◽  
Wild Type ◽  
Bacterial Killing ◽  
E Coli

ABSTRACT We have studied the influence of periplasmic Cu,Zn superoxide dismutase on the intracellular survival of Escherichia colistrains able to invade epithelial cells by the expression of theinv gene from Yersinia pseudotuberculosis but unable to multiply intracellularly. Intracellular viability assays, confirmed by electron microscopy observations, showed that invasive strains of E. coli engineered to increase Cu,Zn superoxide dismutase production are much more resistant to intracellular killing than strains containing only the chromosomalsodC copy. However, we have found only a slight difference in survival within HeLa cells between a sodC-null mutant and its isogenic wild-type strain. Such a small difference in survival correlates with the very low expression of this enzyme in the wild-type strain. We have also observed that acid- and oxidative stress-sensitiveE. coli HB101(pRI203) is more rapidly killed in epithelial cells than E. coli GC4468(pRI203). The high mortality ofE. coli HB101(pRI203), independent of the acidification of the endosome, is abolished by the overexpression of sodC. Our data suggest that oxyradicals are involved in the mechanisms of bacterial killing within epithelial cells and that high-level production of periplasmic Cu,Zn superoxide dismutase provides bacteria with an effective protection against oxidative damage. We propose that Cu,Zn superoxide dismutase could offer an important selective advantage in survival within host cells to bacteria expressing high levels of this enzyme.

scholarly journals Superoxide Dismutase-Deficient Mutants ofHelicobacter pylori Are Hypersensitive to Oxidative Stress and Defective in Host Colonization

2001 ◽  
Vol 69 (6) ◽  
pp. 4034-4040 ◽  
Author(s):  
Richard W. Seyler ◽  
Jonathan W. Olson ◽  
Robert J. Maier
Keyword(s):  
Oxidative Stress ◽  
Superoxide Dismutase ◽  
Virulence Factor ◽  
Type Strain ◽  
Wild Type Strain ◽  
Spontaneous Mutation ◽  
Wild Type ◽  
Sod Activity ◽  
Cell Extracts ◽  
H Pylori

ABSTRACT Superoxide dismutase (SOD) is a nearly ubiquitous enzyme among organisms that are exposed to oxic environments. The single SOD ofHelicobacter pylori, encoded by the sodB gene, has been suspected to be a virulence factor for this pathogenic microaerophile, but mutations in this gene have not been reported previously. We have isolated mutants with interruptions in thesodB gene and have characterized them with respect to their response to oxidative stress and ability to colonize the mouse stomach. The sodB mutants are devoid of SOD activity, based on activity staining in nondenaturing gels and quantitative assays of cell extracts. Though wild-type H. pylori is microaerophilic, the mutants are even more sensitive to O2 for both growth and viability. While the wild-type strain is routinely grown at 12% O2, growth of the mutant strains is severely inhibited at above 5 to 6% O2. The effect of O2 on viability was determined by subjecting nongrowing cells to atmospheric levels of O2 and plating for survivors at 2-h time intervals. Wild-type cell viability dropped by about 1 order of magnitude after 6 h, while viability of the sodBmutant decreased by more than 6 orders of magnitude at the same time point. The mutants are also more sensitive to H2O2, and this sensitivity is exacerbated by increased O2 concentrations. Since oxidative stress has been correlated with DNA damage, the frequency of spontaneous mutation to rifampin resistance was studied. The frequency of mutagenesis of ansodB mutant strain is about 15-fold greater than that of the wild-type strain. In the mouse colonization model, only 1 out of 23 mice inoculated with an SOD-deficient mutant of a mouse-adapted strain became H. pylori positive, while 15 out of 17 mice inoculated with the wild-type strain were shown to harbor the organism. Therefore, SOD is a virulence factor which affects the ability of this organism to colonize the mouse stomach and is important for the growth and survival of H. pylori under conditions of oxidative stress.

scholarly journals Essential Role of Superoxide Dismutase on the Pathogenicity of Erwinia chrysanthemi Strain 3937

2001 ◽  
Vol 14 (6) ◽  
pp. 758-767 ◽  
Author(s):  
Renata Santos ◽  
Thierry Franza ◽  
Marie-Lyne Laporte ◽  
Christele Sauvage ◽  
Danièle Touati ◽  
...  
Keyword(s):  
Superoxide Dismutase ◽  
Superoxide Anion ◽  
Type Strain ◽  
Reverse Genetics ◽  
Wild Type Strain ◽  
Erwinia Chrysanthemi ◽  
Wild Type ◽  
Reading Frame ◽  
E Coli ◽  
Oxidative Damages

The sodA gene from Erwinia chrysanthemi strain 3937 was cloned by functional complementation of an Escherichia coli sodA sodB mutant and sequenced. We identified a 639-bp open reading frame, which encodes a protein that is 85% identical to the E. coli manganese-containing superoxide dismutase MnSOD. Promoter elements of this gene were identified by transcriptional mapping experiments. We constructed an E. chrysanthemi ΔsodA mutant by reverse genetics. The ΔsodA mutation resulted in the absence of a cytoplasmic SOD, which displays the same characteristics as those of MnSOD. The ΔsodA mutant was more sensitive to paraquat than the wild-type strain. This mutant could macerate potato tubers, similar to the wild-type strain. In contrast, when inoculated on African violets, the mutant produced, at most, only small necrotic lesions. If the inoculum was supplemented with the superoxide anion-scavenging metalloporphyrin MnTMPyP or purified SOD and catalase, the ΔsodA mutant was able to macerate the inoculated zone. Generation of superoxide anion by African violet leaves inoculated with E. chrysanthemi was demonstrated with nitroblue tetrazolium as an indicator. Therefore, at the onset of infection, E. chrysanthemi cells encounter an oxidative environment and require active protective systems against oxidative damages such as MnSOD to overcome these types of conditions.

scholarly journals Effects of Mutations of RAD50, RAD51, RAD52, and Related Genes on Illegitimate Recombination in Saccharomyces cerevisiae

Genetics ◽  
1996 ◽  
Vol 142 (2) ◽  
pp. 383-391 ◽  
Author(s):  
Yasumasa Tsukamoto ◽  
Jun-ichi Kato ◽  
Hideo Ikeda
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Quantitative Analysis ◽  
Structural Analysis ◽  
Recombination Rate ◽  
Type Strain ◽  
Negative Selection ◽  
Wild Type Strain ◽  
Illegitimate Recombination ◽  
Wild Type ◽  
In The Wild

Abstract To examine the mechanism of illegitimate recombination in Saccharomyces cerevisiae, we have developed a plasmid system for quantitative analysis of deletion formation. A can1 cyh2 cell carrying two negative selection markers, the CAN1 and CYH2 genes, on a YCp plasmid is sensitive to canavanine and cycloheximide, but the cell becomes resistant to both drugs when the plasmid has a deletion over the CAN1 and CYH2 genes. Structural analysis of the recombinant plasmids obtained from the resistant cells showed that the plasmids had deletions at various sites of the CAN1-CYH2 region and there were only short regions of homology (1-5 bp) at the recombination junctions. The results indicated that the deletion detected in this system were formed by illegitimate recombination. Study on the effect of several rad mutations showed that the recombination rate was reduced by 30-, 10-, 10-, and 10-fold in the rad52, rad50, mre11, and xrs2 mutants, respectively, while in the rud51, 54, 55, and 57 mutants, the rate was comparable to that in the wild-type strain. The rad52 mutation did not affect length of homology at junction sites of illegitimate recombination.

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