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1.
Superoxide radicals and phagocytosis 总被引:15,自引:0,他引:15
Escherichia coli B, grown in iron-rich media, were more resistant toward the aerobic bactericidal action of the formed elements of blood than were comparable iron-deficient cells. The iron replete cells contained 2.5 times more ferrisuperoxide dismutase, 12 times more peroxidase, and 1.5 times more catalase than did the iron-deficient cells. The iron-deficient cells were more susceptible to exogenous O2? and to H2O2 than were iron-replete cells. Cyanide permitted a differentiation between ferrisuperoxide dismutase and catalase or peroxidase since it inhibited the latter peroxide-consuming enzymes but had no effect on the superoxide-utilizing enzyme. In the presence of 2 mm cyanide, the iron-replete E. coli were much more resistant toward phagocytic kill than were the iron-deficient cells even though this level of cyanide completely inhibited catalase and peroxidase. It can be concluded that a large part of the enhanced resistance toward phagocytic kill, exhibited by iron-replete E. coli B, was due to their increased content of the periplasmic ferrisuperoxide dismutase. It follows that O2? is probably an important agent in the killing of phagocytized E. coli B. 相似文献
2.
Endogenous Superoxide Dismutase Levels Regulate Iron-Dependent Hydroxyl Radical Formation in Escherichia coli Exposed to Hydrogen Peroxide
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Michael L. McCormick Garry R. Buettner Bradley E. Britigan 《Journal of bacteriology》1998,180(3):622-625
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 α-(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. 相似文献
3.
Kinetic analysis of superoxide anion production by activated and resident murine peritoneal macrophages 总被引:2,自引:0,他引:2
Using a continuous spectrophotometric assay, we have monitored the formation of superoxide anion (O2?) by activated and resident murine peritoneal macrophages. Macrophages elicited by injection with Corynebacterium parvum, as well as resident macrophages from untreated mice, were kept in suspension culture overnight to eliminate short-lived, contaminating neutrophils. Cytochemical analysis of the cultured macrophages disclosed that essentially all of the activated macrophages reduced nitroblue tetrazolium (NBT) dye vigorously. In contrast, only 18% of the resident macrophages demonstrated vigorous NBT reduction; the remainder of the resident macrophages reduced NBT very weakly. Kinetic analysis of macrophage O2? formation revealed that activated macrophages exposed to phorbol myristate acetate (PMA) produced O2? at a 13-fold greater maximum rate than resident macrophages. The decline in the rate of O2? production with time by activated macrophages was also greater than that of resident macrophages. The data indicate that the greater O2? production by activated macrophage populations is due to (i) the presence of an increased percentage of macrophages that respond to PMA with vigorous O2? production, and (ii) an increased maximum rate of O2? formation by these macrophages. 相似文献
4.
D. N. Karimova I. V. Manukhov E. Yu. Gnuchikh I. F. Karimov D. G. Deryabin 《Applied Biochemistry and Microbiology》2016,52(3):269-276
The effect of reactive oxygen and nitrogen species on lux-biosensors based on the Escherichia coli K12 MG1655 and Salmonella typhimurium LT2 host strains was investigated. The bioactivity of exogenous free radicals to the constitutively luminescent E. coli strain with plasmid pXen7 decreased in the order H2O2 > OCl– > NO? > RОO? > ONOO–> O2?- while the bioluminescence of S. typhimurium strain transformed with this plasmid decreased in the order NO? > H2O2 > ONOO– > RОO? > OCl– > O2?- The cross-reactivity of induced lux-biosensors to reactive oxygen and nitrogen species, the threshold sensitivity and the luminescence amplitude dependences from the plasmid specificity and the host strain were indicated. The biosensors with plasmid pSoxS′::lux possessed a wider range of sensitivity, including H2O2 and OCl–, along with O2?- and NO?. Among the used reactive oxygen and nitrogen species, H2O2 showed the highest induction activity concerning to the plasmids pKatG′::lux, pSoxS′::lux and pRecA′::lux. The inducible lux-biosensors based on S. typhimurium host strain possessed a higher sensitivity to the reactive oxygen and nitrogen species in comparison with the E. coli lux-biosensors. 相似文献
5.
SummaryOxygen (O2)-dependent and O2-independent antimicrobial mechanisms are used by alveolar macrophages (AM) to maintain lung sterility, but these mechanisms are underdeveloped in neonatal AM. Nitric oxide (NO.), a more recently described antimicrobial and immunomodulating molecule, has not been studied in neonatal AM. Lavaged AM from 3-day-old, 10-day-old, maternal and adult rats were treated with or without lipopolysaccharide (LPS) and/or interferon-γ (IFN-γ) and NO. synthase activity was measured as its L-arginine metabolites: NO2?, NO3?, and citrulline. Superoxide anion (O2.-) production by suspended macrophages, initiated by either opsonized zymosan or phorbol, was used as a marker of O2-dependent antimicrobial activity. Lysozyme content of AM was measured as a component of O2-independent antimicrobial activity. Unstimulated 3-day-old macrophages generated >10-fold more NO2? + NO3? than did 10-day-old, maternal or adult AM. Twenty hours after LPS and IFN-γ stimulation, 3-day-old AM produced > 2 times more NO2? and NO3? than did the more mature macrophages. Basal and stimulated O2.- release was similar among 3-day-old, 10-day-old and adult AM, while lysozyme concentrations were > 4-fold higher in adult macrophages compared to AM from 3-day-old pups. Rather than having a role in NO.-dependent antimicrobial activity, we propose that newborn AM have amplified NO. production to modulate their own differentiation and replication after birth. The age-dependent differences in NO. synthase expression by AM may lend insight into the regulation of this important enzyme. 相似文献
6.
Decreased superoxide anion radical production by rat alveolar macrophages following inhalation of ozone or nitrogen dioxide 总被引:2,自引:0,他引:2
exposure of rats to ozone or nitrogen dioxide results in a dose-dependent decrease in superoxide anion radical production (O2?·) by alveolar macrophages isolated from the exposed animals. When alveolar macrophages from ozone-exposed animals were stimulated with phorbol myristate acetate (PMA, a non-phagocytic stimulus of O2?· production) the decrease in O2?· production ranged from 85.9% of control at 3.2 ppm-hrs ozone to 7% of control at 10.5 ppm-hrs. In a similar fashion, O2?· production by PMA-stimulated macrophages from NO2-exposed rates ranged from 78% of control at 18.3 ppm-hrs NO2 down to 14.5% of control at 51 ppm-hrs. Since the viability of the alveolar macrophages obtained from ozone or nitrogen dioxide-exposed animals was 88% or better in all cases as judged by both Trypan blue exclusion and lactate dehydrogenase release, the decreased ability of these cells to produce superoxide anion radical cannot be attributed to a pollutant effect on cell viability. This diminution in superoxide anion radical production by alveolar macrophages from the pollutant-exposed animals might account, in part, for the ability of these 2 air pollutants to potentiate bacterial infections in laboratory animals. 相似文献
7.
Y Keisari 《Cellular immunology》1982,67(1):60-73
Guinea pig peritoneal macrophages (GPPM) exhibited enhanced production of O2? and H2O2, and cytolytic activity toward erythrocytes, in response to reagents such as 12-O-tetradecanoyl-phorbol-13-acetate (TPA), its methylated derivative 4-O-MeTPA, Con A, wheat germ agglutinin (WGA), and opsonized zymosan. In order to examine the possible role of oxidative burst products such as O2? and H2O2 in the cytolytic process, we used reagents and enzymes which influence the balance of O2? and H2O2 outside and inside the GPPM cells. Macrophage-mediated cytolysis (MMC) of erythrocytes in the presence of the activators and modulators was assessed by 51Cr release assay. MMC activated by TPA and 4-O-MeTPA was inhibited by scavengers of H2O2 such as catalase and α-tocopherol, and was augmented by the catalase inhibitor 3-amino-1,2,4-triazole, and by horseradish peroxidase. TPA- and 4-O-MeTPA-activated MMC was only partially inhibited by the O2? scavenger cytochrome c and the enzyme superoxide dismutase and unaffected by cytochalasin D (an inhibitor of phagocytosis). MMC activated by the lectins Con A and WGA was unaffected by the scavengers and enzymes used, but markedly inhibited by cytochalasin D. Activation of MMC by TPA, WGA, and phagocytosis of opsonized zymosan, as well as O2? and H2O2 generation triggered by these reagents, were markedly inhibited by chlorpromazine. The results indicate that GPPM-mediated cytolysis activated by lectins, phorbol ester derivatives, and phagocytosis of opsonized zymosan, is dependent on the generation of oxidative burst products, mainly H2O2. TPA- or 4-O-MeTPA-activated MMC is mainly an extracellular event, while lectin-activated MMC may take place within the macrophages. 相似文献
8.
The cell-free preparations from autotrophieally grown Pseudomonas saccharophila catalyzed the process of electron transport from H2 or various other organic electron donors to either O2 or NO3? with concomitant ATP generation. The respective ratios with H2 and NADH were 0.63 and 0.73, the respective ratios were 0.57 and 0.54. In contrast, the and ratios with succinate were 0.18 and 0.11, respectively. ATP formation coupled to the oxidation of ascorbate, in the absence or presence of added N,N,N′,N′-tetramethyl-p-phenylenediamine or cytochrome c, could not be detected. Various uncouplers inhibited phosphorylation with either O2 or NO3? as terminal electron acceptors without affecting the oxidation of H2 or other substrates. The NADH oxidation at the expense of O2 or NO3? reduction as well as the associated phosphorylation were inhibited by rotenone and amytal. The aerobic and anaerobic H2 oxidation and coupled ATP synthesis, on the other hand, was unaffected by the flavoprotein inhibitors as well as by the NADH trapping system. The NADH, H2, and succinate-linked electron transport to O2 or NO3? and the associated phosphorylations were sensitive, however, to antimycin A or 2-n-nonyl-4-hydroxyquino-line-N-oxide, and cyanide or azide. The data indicated that although the phosphorylation sites 1 and II were associated with NADH oxidation by O2 or NO3?, the energy conservation coupled to H2 oxidation under aerobic or anaerobic conditions appeared to involve site II only. 相似文献
9.
Aquaspirillum magnetotacticum strain MS-1 and two nonmagnetic mutants derived from it reduced C2H2 microaerobically but not anaerobically even with NO3 ?. This organism apparently is not capable of NO3 ?-dependent nitrogen fixation. Cells ofA. magnetotacticum reduced C2H2 at rates comparable to those ofAzospirillum lipoferum grown under similar conditions, but much lower than that ofAzotobacter vinelandii grown aerobically. Cells ofA. magnetotacticum in anaerobic cultures lacking NO3 ? did not reduce C2H2 until O2 was introduced. Optimum rates of C2H2 reduction byA. magnetotacticum were obtained at 200 Pa O2. C2H2 reduction was inhibited by more than 1 kPa O2 or 0.2 mM NO3 ? or NH4 +. These results suggest thatA. magnetotacticum fixes N2 only under microaerobic, N-limited conditions. 相似文献
10.
In the presence of hydrogen peroxide, the heme protein lactoperoxidase is able to oxidize thiocyanate and iodide to hypothiocyanite, reactive iodine species, and the inter(pseudo)halogen cyanogen iodide. The killing efficiency of these oxidants and of the lactoperoxidase-H2O2-SCN?/I? system was investigated on the bioluminescent Escherichia coli K12 strain that allows time-resolved determination of cell viability. Among the tested oxidants, cyanogen iodide was most efficient in killing E. coli, followed by reactive iodine species and hypothiocyanite. Thereby, the killing activity of the LPO-H2O2-SCN?/I? system was greatly enhanced in comparison to the sole application of iodide when I? was applied in two- to twenty-fold excess over SCN?. Further evidence for the contribution of cyanogen iodide in killing of E. coli was obtained by applying methionine. This amino acid disturbed the killing of E. coli mediated by reactive iodine species (partial inhibition) and cyanogen iodide (total inhibition), but not by hypothiocyanite. Changes in luminescence of E. coli cells correlate with measurements of colony forming units after incubation of cells with the LPO-H2O2-SCN?/I? system or with cyanogen iodide. Taken together, these results are important for the future optimization of the use of lactoperoxidase in biotechnological applications. 相似文献
11.
Kuender D. Yang Nancy H. Augustine Men-Fang Shaio John F. Bohnsack Harry R. Hill 《Journal of cellular physiology》1994,158(2):347-353
Previous studies have shown that fibronectin (Fn) enhances phagocytosis and killing of antibody-coated bacteria by neutrophils and macrophages. In an attempt to understand the mechanism of this enhancement, we have investigated the effects of Fn on phagocytosis-related actin organization as well as respiratory burst activity in neutrophils, monocytes and culture-derived macrophages. Employing an NBD-phallacidin flow cytometric analysis of filamentous actin formation, we found that Fn promotes rapid actin polymerization within 30 seconds in neutrophils, monocytes, and macrophages, but not lymphocytes. Enhancement of actin polymerization by Fn was concentration-dependent and mediated by a pertussis toxin- but not cholera toxin- sensitive G protein. Inhibition of protein kinase C by sphingosine (20 μM), calcium influx by verapamil (0.1 mM), or intracellular calcium mobilization by 8-(N, N-diethyl-amino) octyl-3,4,5-trimethoxybenzoate HCI (TMB-8; 0.1 mM) did not block Fn-enhanced actin polymerization in phagocytes. Incubation of neutrophils and macrophages on microtiter plates precoated with Fn suppressed superoxide (O2?) production induced by IgG- and IgA- opsonized group B streptococci. In contrast, Fn significantly enhanced IgA- and IgG-mediated O2? production by freshly isolated monocytes. These data suggest that Fn enhances phagocytosis, presumably through G protein-coupled cytoskeleton reorganization and augments O2? production by circulating monocytes. In contrast, it appears to suppress O2? production by the active phagocytic cells, neutrophils and macrophages. This may result in enhanced phagocytosis and intracellular killing of microorganisms without damaging interstitial tissues. © 1994 Wiley-Liss, Inc. 相似文献
12.
Respiration-driven proton translocation has been studied with the oxidant pulse method for cells of denitrifying Paracoccus denitrificans oxidizing H2 during reduction of O2, NO?3, NO?2 or N2O. A simplified scheme of anaerobic electron transport and associated proton translocation is shown that is consistent with the measured . Furthermore, the kinetics and energetics of NO?3 uptake in whole cells of P. denitrificans were studied. For this purpose, we measured H2 consumption or N2O production after addition of NO?3 to a cell suspension, which indirectly gave information about uptake (and reduction) of NO?3. It was found that a lag phase in H2 consumption or N2O production appeared whenever the membrane potential was dissipated by addition of thiocyanate, carbonyl cyanide m-chlorophenylhydrazone or triphenyl-methylphosphonium bromide. However, these lag phases were not observed when NO?2 was present at the moment of introduction of NO?3. On the basis of these findings we conclude that there are two uptake systems for NO?3. One system is dependent on the proton-motive force and is probably used for initiation of NO?3 uptake. The other is an antiport and its function is to take over NO?3 uptake from the first system. 相似文献
13.
Ana Paula Moreira 《Cellular immunology》2010,263(2):196-203
Paracoccidioidomycosis is caused by the thermally dimorphic fungus Paracoccidioides brasiliensis (P. brasiliensis). Most often, this mycosis runs as a chronic progressive course affecting preferentially the lungs. In vitro fungicidal activity against a high virulent strain of P. brasiliensis by murine peritoneal macrophages preactivated with IFN-γ or TNF-α is high and correlates with increased NO and H2O2 production. Within this context, the purpose of this work was to study the role of suppressor cytokines, such as IL-10 and TGF-β, in this process. Incubation of either IFN-γ or TNF-α with IL-10 inhibits fungicidal activity of these cells. However, TGF-β had no effect on fungicidal activity of IFN-γ or TNF-α-activated macrophages. The suppression of fungicidal activity by IL-10 correlated with the inhibition of NO and H2O2 production supporting the involvement of these metabolites in P. brasiliensis killing. These results suggest that IL-10 production in vivo could represent an evasion mechanism of the fungus to avoid host immune response. 相似文献
14.
O. Cantoni G. Brandi G.F. Schiavano A. Albano F. Cattabeni 《Chemico-biological interactions》1989,70(3-4)
The toxicity of H2O2 in Escherichia coli wild type and superoxide dismutase mutants was investigated under different experimental conditions. Cells were either grown aerobically, and then treated in M9 salts or K medium, or grown anoxically, and then treated in K medium. Results have demonstrated that the wild type and superoxide dismutase mutants display a markedly different sensitivity to both modes of lethality produced by H2O2 (i.e. mode one killing, which is produced by concentrations of H2O2 lower than 5 mM, and mode two killing which results from the insult generated by concentrations of H2O2 higher than 10 mM). Although the data obtained do not clarify the molecular basis of H2O2 toxicity and/or do not explain the specific function of superoxide ions in H2O2-induced bacterial inactivation, they certainly demonstrate that the latter species plays a key role in both modes of H2O2 lethality. A mechanism of H2O2 toxicity in E. coli is proposed, involving the action of a hypothetical enzyme which should work as an O2-• generating system. This enzyme should be active at low concentrations of H2O2 (<5 mM) and high concentrations of the oxidant (>5 mM) should inactivate the same enzyme. Superoxide ions would then be produced and result in mode one lethality. The resistance at intermediate H2O2 concentrations may be dependent on the inactivation of such enzyme with no superoxide ions being produced at levels of H2O2 in the range 5–10 mM. Mode two killing could be produced by the hydroxyl radical in concert with superoxide ions, chemically produced via the reaction of high concentrations of H2O2 (>10 mM) with hydroxyl radicals. The rate of hydroxyl radical production may be increased by the higher availability of Fe2+ since superoxide ions may also reduce trivalent iron to the divalent form. 相似文献
15.
Hydrogen peroxide (H2O2, HP) is a universal toxin that organisms deploy to kill competing or invading cells. Bactericidal action of H2O2 presents several questions. First, the lethal H2O2 concentrations in bacterial cultures are 1000x higher than, for example, those calculated for the phagosome. Second, H2O2-alone kills bacteria in cultures either by mode-one, via iron-mediated chromosomal damage, or by mode-two, via unknown targets, but the killing mode in phagosomes is unclear. Third, phagosomal H2O2 toxicity is enhanced by production of nitric oxide (NO), but in vitro studies disagree: some show NO synergy with H2O2 antimicrobial action, others instead report alleviation. To investigate this “NO paradox,” we treated Escherichia coli with various concentrations of H2O2-alone or H2O2+NO, measuring survival and chromosome stability. We found that all NO concentrations make sublethal H2O2 treatments highly lethal, via triggering catastrophic chromosome fragmentation (mode-one killing). Yet, NO-alone is not lethal, potentiating H2O2 toxicity by blocking H2O2 scavenging in cultures. Catalases represent obvious targets of NO inhibition, and catalase-deficient mutants are indeed killed equally by H2O2-alone or H2O2+NO treatments, also showing similar levels of chromosome fragmentation. Interestingly, iron chelation blocks chromosome fragmentation in catalase-deficient mutants without blocking H2O2-alone lethality, indicating mode-two killing. In fact, mode-two killing of WT cells by much higher H2O2 concentrations is transiently alleviated by NO, reproducing the “NO paradox.” We conclude that NO potentiates H2O2 toxicity by promoting mode-one killing (via catastrophic chromosome fragmentation) by otherwise static low H2O2 concentrations, while transiently suppressing mode-two killing by immediately lethal high H2O2 concentrations. 相似文献
16.
Shiyi He Aiyan Wang Xueping Ning Dongjun Yang Min Ling 《World journal of microbiology & biotechnology》2017,33(6):127
The production of reactive oxygen intermediates (ROI) and reactive nitrogen intermediates (RNI) is an important host defense mechanism in response to infection by Mycobacterium tuberculosis. A variety of genes have been implicated in resistance to ROI and RNI, including noxR1. However, studies in Mycobacterium avium, an important pathogen among nontuberculous mycobacteria, are limited. We aim to investigate the role of a novel gene cloned from M. avium with high similarity to noxR1, noA, in resistance against RNI and ROI in M. tuberculosis. After subcloning noA into vector for expression in E. coli, we performed survival rate analysis in the bacteria transformed with noA (pET-noA) and without noA (pET-his) after exposure to nitrosative stresses by S-nitrosoglutathione (GSNO) and sodium nitrite, and oxidative stresses by H2O2. Compared with pET-his, the survival rate of pET-noA was 1 log10-fold higher after exposure to GSNO and sodium nitrite. We observed 1 log10-fold, 2 log10-fold and 3 log10-fold higher survival rate in pET-noA than pET-his after exposure to H2O2 for 3, 6 and 9 h, respectively. With the combined treatment of H2O2 and GSNO, we found more than 2 log10-fold increase in survival rate in pET-noA comparing with pET-his, suggesting a possible synergistic effect. In summary, noA gene cloned from M. avium has been shown to protect E. coli from both RNI and ROI. 相似文献
17.
Superoxide anion and hydrogen peroxide production by chemically elicited peritoneal macrophages--induction by multiple nonphagocytic stimuli 总被引:19,自引:0,他引:19
The ability of a number of stimulants to activate an oxidative burst (OB) in oil-elicited guinea pig peritoneal exudate macrophages (MPs) was examined. The parameters of the OB were the generation and extracellular release of Superoxide anions (O2?) and hydrogen peroxide (H2O2). We found that: (1) The cocarcinogen and skin irritant phorbol myristate acetate (PMA) was the most potent OB activator—The weak cocarcinogen 4-O-methyl PMA was a proportionally less effective OB activator; (2) The lectins concanavalin A (Con A) and wheat germ agglutinin (WGA), but not soybean, Lotus, and pokeweed lectins, were also quite effective OB activators—The ability of Con A to stimulate O2? production was abolished by succinylation and could be prevented by the presence of α-methyl-D-mannoside; (3) Other stimulators of an OB in MPs were: N-formyl-methionyl peptides, opsonized zymosan, the Ca2+ ionophore A23187, phospholipase C, NaF, antimacrophage antibody, microtubule-disrupting drugs, and sodium nitroprusside—O2? generation induced by A23187 (but not that stimulated by PMA) was dependent on extracellular Ca2+; (4) The amount of O2? produced per cell was higher at low cell densities; (5) The addition of Superoxide dismutase (SOD) to the medium totally prevented the detection of O2? and augmented twice the amount of H2O2 recovered; (6) Pretreatment of MPs with the SOD inhibitor sodium diethyldithiocarbamate had no effect on the release of O2? but blocked H2O2 release in a dose-dependent manner. These data were interpreted as indicating that the bulk of H2O2 was derived by enzymatic dismutation of O2?; (7) The common mechanism by which such a variety of stimuli provoke an OB in MPs was not elucidated. No evidence was found to suggest a role for a cyclic nucleotide messenger. 相似文献
18.
Hidetaka Doi Yasushi Hoshino Kentaro Nakase Yoshihiro Usuda 《Applied microbiology and biotechnology》2014,98(2):629-639
Fatty acids are a promising raw material for substance production because of their highly reduced and anhydrous nature, which can provide higher fermentation yields than sugars. However, they are insoluble in water and are poorly utilized by microbes in industrial fermentation production. We used fatty acids as raw materials for l-lysine fermentation by emulsification and improved the limited fatty acid-utilization ability of Escherichia coli. We obtained a fatty acid-utilizing mutant strain by laboratory evolution and demonstrated that it expressed lower levels of an oxidative-stress marker than wild type. The intracellular hydrogen peroxide (H2O2) concentration of a fatty acid-utilizing wild-type E. coli strain was higher than that of a glucose-utilizing wild-type E. coli strain. The novel mutation rpsA D210Y identified in our fatty acid-utilizing mutant strain enabled us to promote cell growth, fatty-acid utilization, and l-lysine production from fatty acid. Introduction of this rpsA D210Y mutation into a wild-type strain resulted in lower H2O2 concentrations. The overexpression of superoxide dismutase (sodA) increased intracellular H2O2 concentrations and inhibited E. coli fatty-acid utilization, whereas overexpression of an oxidative-stress regulator (oxyS) decreased intracellular H2O2 concentrations and promoted E. coli fatty acid utilization and l-lysine production. Addition of the reactive oxygen species (ROS) scavenger thiourea promoted l-lysine production from fatty acids and decreased intracellular H2O2 concentrations. Among the ROS generated by fatty-acid β-oxidation, H2O2 critically affected E. coli growth and l-lysine production. This indicates that the regression of ROS stress promotes fatty acid utilization, which is beneficial for fatty acids used as raw materials in industrial production. 相似文献
19.
Jung Kon Kim Hack Sun Choi Eungbin Kim Young Sang Lee Yong Ho Kim Si Wouk Kim 《Biotechnology letters》2002,24(17):1397-1400
A novel and highly effective UV-TiO2 photocatalytic reactor was developed for killing microorganisms, including Escherichia coli. Among tested four types of TiO2-immobilized photocatalytic supporters (glass bead, muscovite bead, alginate bead, and TiO2 thin film coated quartz tube), the muscovite bead had a 99.9% percent bactericidal activity within 5 min along with permanent longevity. Adding air bubbles or H2O2 (<50 mg l–1) to the sample solution significantly enhanced the killing activity in that 100% percent of bacterial cells were killed within 3 min. 相似文献
20.
A reaction of the superoxide radical with tetrapyrroles 总被引:1,自引:0,他引:1
Bilirubin and biliverdin were bleached during exposure to the aerobic xanthine oxidase reaction. Enzymic scavenging of O2?, by Superoxide dismutase, inhibited, whereas enzymic scavenging of H2O2, by catalase, did not. Increasing the rate of production of O2? without increasing the turnover rate of xanthine oxidase, by increasing pO2, accelerated the bleaching of the biliverdin. Moreover, a scavenger of OH·, such as benzoate, or an inactivating chelating agent for iron, such as diethylenetriamine pentaacetate or desferrioxamine mesylate, did not inhibit. It follows that O2? can directly attack these tetrapyrroles. Kinetic competition between Superoxide dismutase and bilirubin yielded a value for kbilirubin, O2? = 2.3 × 104 M?1s?1 at pH 8.3 and at 23 °C. A similar experiment for biliverdin yielded a value for kbilirubin, O2? = 7 × 104 M?1s?1. 相似文献