Bacterial defenses against oxidative stress (original) (raw)
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Physiological changes induced in four bacterial strains following oxidative stress
Applied Biochemistry and Microbiology, 2006
1 Aerobic respiration is how bacteria generate metabolic energy. It implicates a four-electron reduction of molecular oxygen ( O 2 ) to water, which can be hazardous to the cell. In particular, an abnormal electron can deviate from the electron transport chain, or cellular enzymes to O 2 can induce the production of reactive oxygen intermediates (ROI) that includes superoxide ( ), hydrogen peroxide ( H 2 O 2 ), and hydroxyl radical (
Variable Bacterial Responses to Oxidative Stress in Different Bacterial Species
Al-Azhar Medical Journal
Background: Living organisms are exposed to oxidative stress due to internal or external stimuli. It results from the imbalance between the production and elimination of reactive oxygen species. This leads to loss of homeostasis. Objective: To test the effect of oxidative stress on the level of the production of reduced glutathione (GSH) as an antioxidant, malondialdehyde (MDA) as a measure of lipid peroxidation, and of the siderophore enterobactin as an oxidative stress response, in different bacterial species. Materials and Methods: H2O2 minimum inhibitory concentration (MIC) was determined in Escherichia coli ATCC 25922 and Klebsiella pneumoniae ATCC 700603, using broth-macrodilution method. The levels of GSH and MDA were measured in E. coli ATCC 25922 and K. pneumoniae ATCC 700603 and in clinical isolates of E. coli, K. pneumoniae and Staphylococcus aureus after exposure to lethal H2O2 concentration, using Glutathione Reduced Kit and Lipid Peroxide-Malondialdehyde Kit, respectively. The level of expression of entC gene, involved in enterobactin biosynthesis, in presence of 0.25 and 0.5 MIC of H2O2 was determined using quantitative reverse transcription-polymerase chain reaction. Results: H2O2 MIC for both E. coli ATCC 25922 and K. pneumoniae ATCC 700603 was 1.5 mM. Exposure of E. coli to H2O2 resulted in a significant increase in GSH (p=0.0001) and MDA (p=0.0001) levels. However, in K. pneumoniae, a significant decrease in the GSH (p=0.0001) and MDA levels (p=0.0001) was recorded upon H2O2 exposure. No change in MDA and GSH levels was detected in S. aureus isolates exposed to H2O2. The expression of entC gene in both E. coli ATCC 25922 and K. pneumoniae ATCC 700603 was reduced in presence of 0.25 and 0.5 H2O2 MIC. Conclusion: Bacteria responded differently to oxidative stress, with S. aureus bacteria as the least affected by oxidative stress. Enterobactin role in oxidative stress needs reevaluation.
Oxidative Stress Response in Bacteria: A Review
Fine Focus
Oxidative Stress Response (OSR) is a defense mechanism used to maintain cellular homeostasis after an increase in levels of Reactive Oxygen Species (ROS). Due to ROS, cell components are vulnerable to damage including the membrane and DNA - which can impact essential functions and lead to cellular death. Without repair, damages caused by ROS have the potential to disrupt cell function in an irreparable manner. Bacterial cells respond to ROS using both endogenous and exogenous pathways depending on their method of metabolism and evolutionary ability. Bacteria have developed regulatory mechanisms to contain damage and are also known to use antioxidants as defense. In this review we will cover the damage induced by ROS to different cellular structures, and mechanisms of OSR used by bacterial cells to promote survival.
Oxidative stress and mechanisms of protection against it in bacteria
Biochemistry. Biokhimii͡a, 2001
In the review contemporary data on the effects of oxidative stresses of various kinds in bacteria are summarized. A general theory of oxidative stress, peculiarities of oxidative stress in eukaryotes and prokaryotes, and natural and induced oxidative stresses are described. Data on the mechanisms of protection against oxidative stress are given, including prevention of the generation of oxidative stress, prevention of propagation of free radical chain reactions, and the mechanisms of repair of damaged DNA. The regulation of effector genes via redox-sensitive iron-containing proteins is analyzed. Special attention is given to the expression of so-called antioxidant and associated enzymes as protection mechanisms and to the space-time organization of the response of bacteria to oxidative stress.
Journal of bacteriology, 1989
Escherichia coli treated with nontoxic levels of the superoxide-generating redox-cycling agents menadione and paraquat showed dramatic changes in protein composition as monitored by two-dimensional gel analysis. The distribution of proteins synthesized after treatment with these agents overlapped significantly with that seen after hydrogen peroxide treatment, and it included all the proteins in the oxyR regulon. The redox-cycling agents also elicited the synthesis of at least 33 other proteins that were not seen with hydrogen peroxide, including three heat shock proteins, the Mn-containing superoxide dismutase, the DNA repair protein endonuclease IV, and glucose-6-phosphate dehydrogenase. At least some of these redox-inducible proteins appear to be part of a specific response to intracellular superoxide. E. coli is thus equipped with a network of inducible responses against oxidative damage, controlled in multiple regulatory pathways.
Anaerobe, 2003
Gram-negative anaerobes in the genus Bacteroides are the predominant members of the GI-tract microflora where they play an important role in normal intestinal physiology. Bacteroides spp. also are significant opportunistic pathogens responsible for an array of intra-abdominal and other infections. Bacteroides fragilis is the most common anaerobic pathogen and it possesses virulence factors such as a capsule and neuraminidase that contribute to its success as a pathogen. Infection occurs when organisms escape from the anaerobic colon to aerobic sites such as the peritoneum where O 2 concentrations average 6%. Thus in addition to the classic virulence factors, resistance to oxidative stress is essential and may be involved in the initiation and persistence of infection. In fact, B. fragilis is highly O 2 tolerant, surviving extended periods (>24 h) of O 2 exposure without a significant affect on viability. For protection against this oxidative stress B. fragilis mounts a complex physiological response that includes induction of >28 proteins involved in detoxification of oxygen radicals, protection of macromolecules, and adaptive physiology. One experimental strategy used to characterize this oxidative stress response is the direct detection of genes and proteins induced during exposure to O 2 or H 2 O 2 . The methods employed have included RNA differential display to capture unique mRNA transcripts produced during oxidative stress, and native or 2D-gel electrophoresis to isolate and identify newly formed stress-induced proteins. Using these and other approaches a wide array of genes induced by oxidative stress have been discovered. These include genes for catalase, superoxide dismutase, thioredoxin-peroxidase, p20-peroxidase, cytochrome c peroxidase, Dps, alkyl hydroperoxidase, aerobic ribonucleotide reductase, ruberythrin, starch utilization, aspartate decarboxylase, and an RNA binding protein. The genes encoding these activities fall into three regulatory classes: (1) induced by O 2 only, (2) induced by H 2 O 2 only, and (3) induced by either O 2 or H 2 O 2 . Such a complex regulatory response will likely involve multiple regulators. Thus far one regulator has been identified, OxyR, which controls a subset of the class 3 genes that are induced by either O 2 or H 2 O 2 . OxyR responds rapidly to oxidative stress and transcriptional analyses have shown that OxyR-controlled genes are activated by as little as 0.5% O 2 or 10 mM H 2 O 2 . Maximal expression of most OxyR regulon genes was reached at 50 mM H 2 O 2 and 2% O 2 . These oxidant concentrations are similar to environmental levels that would be experienced by the organisms in tissues outside of the colon suggesting that the OxyR regulon would be induced during the course of an infection. r
Non-lethal exposure to H2O2 boosts bacterial survival and evolvability against oxidative stress
Unicellular organisms have the prevalent challenge to survive under oxidative stress of reactive oxygen species (ROS) such as hydrogen peroxide (H2O2). ROS are present as by-products of photosynthesis and aerobic respiration. These reactive species are even employed by multicellular organisms as potent weapons against microbes. Although bacterial defences against lethal and sub-lethal oxidative stress have been studied in model bacteria, the role of fluctuating H2O2 concentrations remains unexplored. It is known that sub-lethal exposure of Escherichia coli to H2O2 results in enhanced survival upon subsequent exposure. Here we investigate the priming response to H2O2 at physiological concentrations. The basis and the duration of the response (memory) were also determined by time-lapse quantitative proteomics. We found that a low level of H2O2 induced several scavenging enzymes showing a long half-life, subsequently protecting cells from future exposure. We then asked if the phenotypi...
Canadian Journal of Microbiology, 1988
1988. Response of hydroperoxidase and superoxide dismutase deficient mutants of Escherichia coli K-12 to oxidative stress. Can. J. Microbiol. 34: 1171 -1176. In Escherichia coli, the coordinate action of two antioxidant enzymes, superoxide dismutase and hydroperoxidase (catalase), protect the cell from the deleterious effects of oxyradicals generated during normal aerobic respiration. To evaluate the relative importance of these two classes of enzymes, strains of E. coli deficient in superoxide dismutase and (or) hydroperoxidase were constructed by generalized transduction and their physiological responses to oxygen and oxidant stress examined. Superoxide dismutase was found to be more important than hydroperoxidase in preventing oxygen-dependent growth inhibition and mutagenesis, and in reducing sensitivity to redox-active compounds known to generate the superoxide anion. However, both types of enzymes were required for an effective defense against chemical oxidants that generate superoxide radicals and hydrogen peroxide. SCHELLHORN, H. E., et HASSAN, H. M. 1988. Response of hydroperoxidase and superoxide dismutase deficient mutants of Escherichia coli K-12 to oxidative stress. Can. J. Microbiol. 34 : 1171 -1176.