Photochemical production of superoxide and hydrogen peroxide from natural organic matter

Garg, Shikha; Rose, Arthur W.; Waite, T. David

doi:10.1016/j.gca.2011.05.014

Cited by 150 publications

(215 citation statements)

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“…As described earlier (Garg et al, 2011b), this occurs due to interaction of • 2 HO with organic radicals (depicted as R ▪ ) generated on irradiation of SRFA (reaction 8). As shown in Figure EA- The rate constant for generation of radical R ▪ (reaction 7) and its bimolecular decay rate constant (reaction 9) was assumed to be pH-independent with values reported in our earlier work (Garg et al, 2011b) used here.…”

Section: Oxidative Superoxide Sinkmentioning

confidence: 87%

“…The electron accepting and electron donating capacities of NOM have been recently investigated using electrochemical oxidation and reduction methods and been attributed to the presence of quinone and phenolic functional groups respectively (Aeschbacher et al, 2012). Quinone functional groups are able to exist in multiple redox states and have been implicated in i) the electron transfer reactions that result in reactive oxygen species (ROS) formation in natural waters (Cooper and Zika, 1983;Garg et al, 2011b;Goldstone and Voelker, 2000), ii) the optical properties of NOM (Del Vecchio and Blough, 2004) and iii) the redox transformations of trace metals such as copper and, of particular interest here, iron in natural waters.…”

Section: Introductionmentioning

confidence: 99%

“…On irradiation of SRFA, superoxide (denoting both • 2 HO and 2 O  with the relative proportions of these acid-base pairs present dependent on the particular pH) is generated on reduction of dioxygen by semiquinone radicals ( Q  ) formed on reduction of an excited quinone-triplet (or quinone-water exciplex) by an electron donor (D) molecule (Garg et al, 2011b). Superoxide so formed disproportionates to form H 2 O 2 or oxidizes in the presence of a light-generated organic radical (R ▪ ) to form dioxygen.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Mechanistic insights into iron redox transformations in the presence of natural organic matter: Impact of pH and light

Garg

Jiang

Waite

2015

Geochimica et Cosmochimica Acta

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Section: Oxidative Superoxide Sinkmentioning

confidence: 87%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Mechanistic insights into iron redox transformations in the presence of natural organic matter: Impact of pH and light

Garg

Jiang

Waite

2015

Geochimica et Cosmochimica Acta

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“…Hydrogen peroxide is produced by dismutation of O 2 ·− (reaction 11) [20]. Quantum yields for H 2 O 2 production are also wavelengthdependent and at ca.…”

Section: Photochemistry Of Hsmentioning

confidence: 99%

Photogeneration of Reactive Oxygen Species by SBO and Application in Waste-Water Treatment

Carlos

Martire

2015

SpringerBriefs in Molecular Science

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Soluble bio-based substances (SBO) extracted from urban bio-wastes have similar chemical properties to humic substances (HS) present in natural waters and soils. Therefore, SBO are also expected to have photochemical properties similar to HS. In this chapter, a summary of the photochemistry of HS is presented along with the recent advances related to the photogeneration of reactive species upon irradiation of aqueous solutions of SBO and some examples of pollutant degradation photo-induced by SBO.

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“…Superoxide and hydrogen peroxide can also be generated photochemically from natural organic matter and in aqueous solutions of aromatic compounds (22,23). Although Acinetobacter species, which belong to a class of ␥-proteobacteria, are widely distributed in nature, and their pathogenic species are of great concern for human disease, the genetics and physiology of Acinetobacter species are poorly explored.…”

mentioning

confidence: 99%

Lineage-specific SoxR-mediated Regulation of an Endoribonuclease Protects Non-enteric Bacteria from Redox-active Compounds

Kim

Park

Imlay

et al. 2017

Journal of Biological Chemistry

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Edited by F. Peter GuengerichBacteria use redox-sensitive transcription factors to coordinate responses to redox stress. The [2Fe-2S] cluster-containing transcription factor SoxR is particularly tuned to protect cells against redox-active compounds (RACs). In enteric bacteria, SoxR is paired with a second transcription factor, SoxS, that activates downstream effectors. However, SoxS is absent in nonenteric bacteria, raising questions as to how SoxR functions. Here, we first show that SoxR of Acinetobacter oleivorans displayed similar activation profiles in response to RACs as did its homolog from Escherichia coli but controlled a different set of target genes, including sinE, which encodes an endoribonuclease. Expression, gel mobility shift, and mutational analyses indicated that sinE is a direct target of SoxR. Redox potentials and permeability of RACs determined optimal sinE induction. Bioinformatics suggested that only a few ␥-and ␤-proteobacteria might have SoxR-regulated sinE. Purified SinE, in the presence of Mg 2؉ ions, degrades rRNAs, thus inhibiting protein synthesis. Similarly, pretreatment of cells with RACs demonstrated a role for SinE in promoting persistence in the presence of antibiotics that inhibit protein synthesis. Our data improve our understanding of the physiology of soil microorganisms by suggesting that both non-enteric SoxR and its target SinE play protective roles in the presence of RACs and antibiotics.Oxidative stress is an unavoidable consequence of aerobic and anaerobic metabolism when cells are exposed to O 2 . Bacteria have evolved to harbor defense mechanisms against various reactive oxygen species (ROS).4 Bacteria protect themselves by activating ROS-sensing transcription factors, including OxyR and PerR, that detect hydrogen peroxide (H 2 O 2 ) using cysteine residues and iron, respectively, and SoxR, which responds to superoxide or redox-active compounds (RACs) using a [2Fe-2S] cluster (1-3). Bacteria can produce many natural RACs, such as pyocyanin (PYO), actinorhodin, and plumbagin (PL), that act as antibiotics, toxic compounds, and quorum signals (4). RACs can generate toxic doses of ROS inside cells by mediating electron transfer from redox enzymes to O 2 . When Escherichia coli is exposed to RACs, SoxR is activated by the oxidation of its [2Fe-2S] cluster, and it subsequently induces the transcription of soxS (5-8). SoxS then induces the transcription of numerous genes involved in the repair of oxidatively damaged enzymes and DNA and the elimination of ROS (9 -12). However, the E. coli-SoxRS paradigm does not apply to nonenteric bacteria because of the absence of SoxS and no induction of many known E. coli SoxRS regulon (13-18). Surprisingly, activated SoxR can directly induce several genes (lpxC, aroF, sodA, and mgtA) in E. coli by binding their promoters without soxS (16). SoxR can be activated directly by RACs rather than by superoxide, as evidenced by the fact that RACs can oxidize the [2Fe-2S] 1ϩ cluster of SoxR even under anaerobic conditions (1, 2, 12). Activated S...

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Photochemical production of superoxide and hydrogen peroxide from natural organic matter

Cited by 150 publications

References 54 publications

Mechanistic insights into iron redox transformations in the presence of natural organic matter: Impact of pH and light

Mechanistic insights into iron redox transformations in the presence of natural organic matter: Impact of pH and light

Photogeneration of Reactive Oxygen Species by SBO and Application in Waste-Water Treatment

Lineage-specific SoxR-mediated Regulation of an Endoribonuclease Protects Non-enteric Bacteria from Redox-active Compounds

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