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Journal ArticleDOI

Endogenous Superoxide Dismutase Levels Regulate Iron-Dependent Hydroxyl Radical Formation in Escherichia coli Exposed to Hydrogen Peroxide

01 Feb 1998-Journal of Bacteriology (American Society for Microbiology)-Vol. 180, Iss: 3, pp 622-625
TL;DR: The hypothesis that a resulting increase in .OH formation generated by Fenton chemistry is responsible for the observed enhancement of DNA damage and the increased susceptibility to H2O2-mediated killing seen in these mutants lacking SOD is supported.
Abstract: Aerobic organisms contain antioxidant enzymes, such as superoxide dismutase (SOD) and catalase, to protect them from both direct and indirect effects of reactive oxygen species, such as O2.- and H2O2. Previous work by others has shown that Escherichia coli mutants lacking SOD not only are more susceptible to DNA damage and killing by H2O2 but also contain larger pools of intracellular free iron. The present study investigated if SOD-deficient E. coli cells are exposed to increased levels of hydroxyl radical (.OH) as a consequence of the reaction of H2O2 with this increased iron pool. When the parental E. coli strain AB1157 was exposed to H2O2 in the presence of an alpha-(4-pyridyl-1-oxide)-N-tert-butyl-nitrone (4-POBN)-ethanol spin-trapping system, the 4-POBN-.CH(CH3)OH spin adduct was detectable by electron paramagnetic resonance (EPR) spectroscopy, indicating .OH production. When the isogenic E. coli mutant JI132, lacking both Fe- and Mn-containing SODs, was exposed to H2O2 in a similar manner, the magnitude of .OH spin trapped was significantly greater than with the control strain. Preincubation of the bacteria with the iron chelator deferoxamine markedly inhibited the magnitude of .OH spin trapped. Exogenous SOD failed to inhibit .OH formation, indicating the need for intracellular SOD. Redox-active iron, defined as EPR-detectable ascorbyl radical, was greater in the SOD-deficient strain than in the control strain. These studies (i) extend recent data from others demonstrating increased levels of iron in E. coli SOD mutants and (ii) support the hypothesis that a resulting increase in .OH formation generated by Fenton chemistry is responsible for the observed enhancement of DNA damage and the increased susceptibility to H2O2-mediated killing seen in these mutants lacking SOD.

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Citations
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Journal ArticleDOI
TL;DR: Effects of paraquat dichloride (PQ) on the laccase (LAC) activity and some biochemical parameters of Trametes versicolor and Abortiporus biennis strains belonging to white rot Basidiomycetes fungi were examined.

68 citations

Journal ArticleDOI
TL;DR: Data support the hypothesis that transition metal-mediated HO.

61 citations

Journal ArticleDOI
TL;DR: The antioxidative properties in Lactobacillus sake strains from different food origins were determined at low temperature and upon exposure to oxygen levels between 20 and 90% O(2), and it is concluded that its removal is essential for cell protection at elevated O( 2) conditions.
Abstract: The ability of bacteria to overcome oxidative stress is related to the levels and types of antioxidative mechanisms which they possess. In this study, the antioxidative properties in Lactobacillus sake strains from different food origins were determined at low temperature (8°C) and upon exposure to oxygen levels between 20 and 90% O2. The L. sake strains tested grew well at 8°C and in the presence of 20% O2, however, most of the strains could not grow at O2 levels as high as 50 and/or 90%. Cell-free extracts of all strains possessed certain levels of hydroxyl radical scavenging, metal chelating and reducing capacities essential for growth of cells at ambient O2. At elevated O2 concentrations, a high H2O2 splitting capacity and low specific rates of H2O2 production were demonstrated in the O2-insensitive strain L. sake NCFB 2813, which could grow at elevated O2 conditions. Although H2O2 was generated in the O2-sensitive L. sake DSM 6333 at levels which were not directly toxic to the cells (<0.2 mM), we can conclude that its removal is essential for cell protection at elevated O2 conditions.

59 citations


Cites background from "Endogenous Superoxide Dismutase Lev..."

  • ...In bacteria, generation of the HO radical is facilitated by the presence of O2 , H2O2 and free iron [4,5]....

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Journal ArticleDOI
TL;DR: In this paper, the role of hydrogen peroxide in the antimicrobial activity of Lactobacilli was investigated in a series of experiments carried out in order to elucidate the role H2O2 in antimicrobial activities.
Abstract: This study presents a series of experiments carried out in order to elucidate the role of H2O2 in antimicrobial activity of lactobacilli. Vaginal swabs were collected from 60 premenopausal women and checked for pH and Nugent score, and Lactobacillus species were cultured, phenotyped and genotyped. The main outcome measures involved: (1) species of vaginal lactobacilli most effective in liberating H2O2, (2) minimal microbicidal concentrations of added H2O2, (3) kinetics of H2O2 liberation in relation to oxygen tension, (4) antimicrobial activity of pure H2O2 versus one produced by selected vaginal lactobacilli and the total activity of their culture supernatants. Results showed that H2O2 was liberated especially by: Lactobacillus delbrueckii, Lactobacillus acidophilus, Lactobacillus crispatus, Lactobacillus johnsonii and L. gasseri. Hydrogen peroxide reached concentrations from 0.05 to 1.0 mM, which under intensive aeration increased even up to 1.8 mM. Microorganisms related to vaginal pathologies show varied resistance to the action of pure H2O2. Most potent inhibitory activity against bacteria and yeasts was presented by Lactobacillus culture supernate producing H2O2, followed by the nonproducing strain and pure H2O2. To conclude - the antimicrobial activity of lactobacilli is a summation of various inhibitory mechanisms in which H2O2 plays some but not a crucial role, in addition to other substances.

57 citations

Journal ArticleDOI
TL;DR: By discussing various bacterial mutants classified according to their in vitro sensitivity to superoxide, this work exemplifies the complex mechanisms that Salmonella has evolved to cope with superoxide stress.

55 citations

References
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Book
13 Jun 1985
TL;DR: 1. Oxygen is a toxic gas - an introduction to oxygen toxicity and reactive species, and the chemistry of free radicals and related 'reactive species'
Abstract: 1. Oxygen is a toxic gas - an introductionto oxygen toxicity and reactive species 2. The chemistry of free radicals and related 'reactive species' 3. Antioxidant defences Endogenous and Diet Derived 4. Cellular responses to oxidative stress: adaptation, damage, repair, senescence and death 5. Measurement of reactive species 6. Reactive species can pose special problems needing special solutions. Some examples. 7. Reactive species can be useful some more examples 8. Reactive species can be poisonous: their role in toxicology 9. Reactive species and disease: fact, fiction or filibuster? 10. Ageing, nutrition, disease, and therapy: A role for antioxidants?

21,528 citations


"Endogenous Superoxide Dismutase Lev..." refers background in this paper

  • ...rapidly reacts with itself (dismutes) to form H2O2 (7)....

    [...]

  • ...Although the aerobic metabolism of bacteria optimally results in the near simultaneous four-electron reduction of O2 to H2O, a variable percentage of O2 reduction occurs initially via either one-electron reduction of O2 to superoxide (O2 ) or divalent reduction to H2O2 (7)....

    [...]

Journal ArticleDOI
03 Jun 1988-Science
TL;DR: It is proposed that the cell may also decrease such toxicity by diminishing available NAD(P)H and by utilizing oxygen itself to scavenge active free radicals into superoxide, which is then destroyed by superoxide dismutase.
Abstract: A major portion of the toxicity of hydrogen peroxide in Escherichia coli is attributed to DNA damage mediated by a Fenton reaction that generates active forms of hydroxyl radicals from hydrogen peroxide, DNA-bound iron, and a constant source of reducing equivalents. Kinetic peculiarities of DNA damage production by hydrogen peroxide in vivo can be reproduced by including DNA in an in vitro Fenton reaction system in which iron catalyzes the univalent reduction of hydrogen peroxide by the reduced form of nicotinamide adenine dinucleotide (NADH). To minimize the toxicity of oxygen radicals, the cell utilizes scavengers of these radicals and DNA repair enzymes. On the basis of observations with the model system, it is proposed that the cell may also decrease such toxicity by diminishing available NAD(P)H and by utilizing oxygen itself to scavenge active free radicals into superoxide, which is then destroyed by superoxide dismutase.

1,997 citations


"Endogenous Superoxide Dismutase Lev..." refers background in this paper

  • ...Pretreatment of the JI132 (SOD-deficient) bacteria with DFO greatly reduced the magnitude of OH generation, confirming that it arose as a consequence of Fenton chemistry, as iron bound to DFO is no longer available for this redox chemistry (10)....

    [...]

Journal ArticleDOI
TL;DR: Aerotolerant anaerobes, which survive exposure to air and metabolize oxygen to a limited extent but do not contain cytochrome systems, were found to be devoid of catalase activity but did exhibit superoxide dismutase activity.
Abstract: The distribution of catalase and superoxide dismutase has been examined in various micro-organisms. Strict anaerobes exhibited no superoxide dismutase and, generally, no catalase activity. All aerobic organisms containing cytochrome systems were found to contain both superoxide dismutase and catalase. Aerotolerant anaerobes, which survive exposure to air and metabolize oxygen to a limited extent but do not contain cytochrome systems, were found to be devoid of catalase activity but did exhibit superoxide dismutase activity. This distribution is consistent with the proposal that the prime physiological function of superoxide dismutase is protection of oxygen-metabolizing organisms against the potentially detrimental effects of the superoxide free radical, a biologically produced intermediate resulting from the univalent reduction of molecular oxygen.

974 citations


"Endogenous Superoxide Dismutase Lev..." refers background in this paper

  • ...Most bacteria, including Escherichia coli, contain superoxide dismutase (SOD) and catalase as means of eliminating O2 z2 and H2O2, respectively (16, 17)....

    [...]

Journal ArticleDOI
TL;DR: This presentation discusses the role of catalytic metals in free radical-mediated oxidations, ascorbate as both a pro-oxidant and an antioxidant, use of asCorbate to determine adventitious catalytic metal concentrations, and uses of ascorBate radical as a marker of oxidative stress.
Abstract: Trace levels of transition metals can participate in the metal-catalyzed Haber-Weiss reaction (superoxide-driven Fenton reaction) as well as catalyze the oxidation of ascorbate. Generally ascorbate is thought of as an excellent reducing agent; it is able to serve as a donor antioxidant in free radical-mediated oxidation processes. However, as a reducing agent it is also able to reduce redox-active metals such as copper and iron, thereby increasing the pro-oxidant chemistry of these metals. Thus ascorbate can serve as both a pro-oxidant and an antioxidant. In general, at low ascorbate concentrations, ascorbate is prone to be a pro-oxidant, and at high concentrations, it will tend to be an antioxidant. Hence there is a crossover effect. We propose that the "position" of this crossover effect is a function of the catalytic metal concentration. In this presentation, we discuss: (1) the role of catalytic metals in free radical-mediated oxidations; (2) ascorbate as both a pro-oxidant and an antioxidant; (3) catalytic metal catalysis of ascorbate oxidation; (4) use of ascorbate to determine adventitious catalytic metal concentrations; (5) use of ascorbate radical as a marker of oxidative stress; and (6) use of ascorbate and iron as free radical pro-oxidants in photodynamic therapy of cancer.

851 citations

Journal ArticleDOI
TL;DR: In this article, the authors show that the level of loose iron in severely superoxide-stressed cells greatly exceeds that of unstressed cells, and that both growth defects and DNA damage caused by superoxide ensue from its ability to damage a subset of iron-sulfur clusters.
Abstract: Superoxide promotes hydroxyl-radical formation and consequent DNA damage in cells of all types. The long-standing hypothesis that it primarily does so by delivering electrons to adventitious iron on DNA was refuted by recent studies in Escherichia coli. Alternative proposals have suggested that superoxide may accelerate oxidative DNA damage by leaching iron from storage proteins or enzymic [4Fe-4S] clusters. The released iron might then deposit on the surface of the DNA, where it could catalyze the formation of DNA oxidants using other electron donors. The latter model is affirmed by the experiments described here. Whole-cell electron paramagnetic resonance demonstrated that the level of loose iron in superoxide-stressed cells greatly exceeds that of unstressed cells. Bacterial iron storage proteins were not the major source for free iron, since superoxide also increased iron levels in mutants lacking these iron storage proteins. However, overproduction of an enzyme containing a labile [4Fe-4S] cluster dramatically increased the free iron content of cells when they were growing in air. The rates of spontaneous mutagenesis and DNA damage from exogenous H2O2 increased commensurately. It is striking that both growth defects and DNA damage caused by superoxide ensue from its ability to damage a subset of iron–sulfur clusters.

803 citations

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How do you play sod?

Exogenous SOD failed to inhibit·OH formation, indicating the need for intracellular SOD.