Avoiding high-valent iron intermediates: Superoxide reductase and rubrerythrin

Kurtz, Donald M.

doi:10.1016/j.jinorgbio.2005.12.017

Cited by 89 publications

(115 citation statements)

References 145 publications

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“…Rubrerythrins provide protection against hydrogen peroxidemediated oxidative stress 28 and have been suggested to play a role in shielding the highly oxygen-sensitive nitrogenase protein from oxidative damage 29 . We observed that both the nitrogenase proteins and Rbr were detected with significantly lower protein concentrations during diazotrophy-inhibiting conditions (that is, energy limitation caused by sulfide starvation; Supplementary Fig.…”

Section: Resultsmentioning

confidence: 99%

Nitrogen fixation in a chemoautotrophic lucinid symbiosis

et al. 2016

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The shallow water bivalve Codakia orbicularis lives in symbiotic association with a sulfur-oxidizing bacterium in its gills. The endosymbiont fixes CO 2 and thus generates organic carbon compounds, which support the host's growth. To investigate the uncultured symbiont's metabolism and symbiont-host interactions in detail we conducted a proteogenomic analysis of purified bacteria. Unexpectedly, our results reveal a hitherto completely unrecognized feature of the C. orbicularis symbiont's physiology: the symbiont's genome encodes all proteins necessary for biological nitrogen fixation (diazotrophy). Expression of the respective genes under standard ambient conditions was confirmed by proteomics. Nitrogenase activity in the symbiont was also verified by enzyme activity assays. Phylogenetic analysis of the bacterial nitrogenase reductase NifH revealed the symbiont's close relationship to free-living nitrogen-fixing Proteobacteria from the seagrass sediment. The C. orbicularis symbiont, here tentatively named 'Candidatus Thiodiazotropha endolucinida', may thus not only sustain the bivalve's carbon demands. C. orbicularis may also benefit from a steady supply of fixed nitrogen from its symbiont-a scenario that is unprecedented in comparable chemoautotrophic symbioses. Mutualistic associations between marine invertebrates and sulfur-oxidizing (thiotrophic) bacteria are a well-documented and widespread phenomenon in a variety of sulfidic habitats ranging from hydrothermal vents to shallow-water coastal ecosystems 1-3 . Thioautotrophic symbionts generate energy through sulfide oxidation and provide their hosts with organic carbon. In the Lucinidae, a diverse family of marine bivalves, all members are obligatorily dependent on their bacterial gill endosymbionts after larval development and metamorphosis 4 . The shallowwater lucinid Codakia orbicularis, which lives in the sediment beneath the tropical seagrass Thalassia testudinum along the Caribbean and Western Atlantic coast 5 , harbours a single species of endosymbionts in its gills 6 . The symbiont has been shown to be newly acquired by each clam generation 7,8 from a pool of freeliving symbiosis-competent bacteria in the environment 9 , rather than being inherited from clam parents. C. orbicularis appears not to release its endosymbionts, even under adverse conditions, but can digest them as a source of nutrition [10][11][12] . Moreover, bacterial cell division seems to be inhibited inside the host tissue. The majority of the symbiont population was shown to be polyploid (that is, containing multiple genome copies), while dividing symbiont cell stages are very rarely observed in host bacteriocytes 13 . The host undoubtedly benefits from the symbiont both by way of detoxification of its sulfidic environment and by supply of organic compounds through the bacterial Calvin-Benson cycle. It remains questionable, however, whether the symbiont gains any advantage from this association in evolutionary terms 11 .Biological nitrogen fixation (diazotrophy) is the conversion of ...

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Section: Resultsmentioning

confidence: 99%

Nitrogen fixation in a chemoautotrophic lucinid symbiosis

et al. 2016

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“…Whereas the specific involvement of desulforedoxin in an electron transport chain remains to be documented, in the case of sulfate reducing bacteria, rubredoxin is thought to act as an electron relay between the NADH:rubredoxin oxidoreductase (Nro) and several metalloproteins involved in ROS detoxification [10]. This is the case of SOR, but also of rubrerythrin (Rbr), involved in hydrogen peroxide elimination through its peroxidase activity [7] and rubredoxin:oxygen oxidoreductase (Roo) [34], an oxygen reductase that decreases the oxygen concentration within the cell. The detoxifying enzymes SOR, Rbr and Roo could then appear to be in competition for their electron donor rubredoxin.…”

Section: Discussionmentioning

confidence: 99%

“…Cells express very efficient antioxidant systems which detoxify these species [1,2]. In the case of the superoxide radical, only two classes of enzymes able to detoxify it have been described: the superoxide dismutase (SOD) [3], expressed in almost all cells living in contact with oxygen, and the more recently discovered superoxide reductase (SOR) which has been found in some microaerophilic and anaerobic bacteria [4][5][6][7][8][9]. The presence of antioxidant systems in anaerobic bacteria, in particular those living in close contact with aerobic biotopes, allows them to survive when they are transiently or accidentally exposed to oxygen [10].…”

Section: Introductionmentioning

confidence: 99%

Intermolecular electron transfer in two-iron superoxide reductase: a putative role for the desulforedoxin center as an electron donor to the iron active site

et al. 2011

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“…Other significantly upregulated genes included Mn-Fe superoxide dismutase (sodA), desulfoferrodoxin (dfx), rubredoxin (rub) and rubrerythrin (rbr) ( Table 2). The proteins encoded by these genes are thought to be involved in radical detoxification using superoxide dismutase and superoxide reductase systems (Brumlik and Voordouw, 1989;Voordouw and Voordouw, 1998;Jenney et al, 1999;Silva et al, 1999;Kurtz, 2006).…”

Section: Quantifying Expression Of Geobacter Species Pj Mouser Et Almentioning

confidence: 99%

Quantifying expression of Geobacter spp. oxidative stress genes in pure culture and during in situ uranium bioremediation

et al. 2009

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As part of an effort to diagnose the physiological status of Geobacter species during in situ bioremediation of uranium-contaminated groundwater, transcript levels for two genes potentially associated with oxidative stress, cydA and sodA, were quantified throughout a bioremediation field study in Rifle, CO, USA. Despite the accumulation of Fe(II) in the groundwater, which is inconsistent with the presence of dissolved oxygen, both genes were highly expressed during the bioremediation process. Therefore, the response to oxidative stress was further evaluated with Geobacter uraniireducens, an isolate from the Rifle site. When G. uraniireducens cultured with fumarate as the electron acceptor was exposed to 5% oxygen for 8 h, there was a significant increase in cydA and sodA transcripts as well as other genes associated with oxygen respiration or oxidative stress. Oxygen-exposed cells had lower transcript abundance for genes associated with anaerobic respiration, metabolism and motility. Short-term oxygen exposure had little impact on cydA transcript levels, as more than 1 h was required for increases to levels comparable to the subsurface. Abundance of cydA and sodA transcripts for the isolate G. sulfurreducens were always higher in cells cultured with Fe(III) compared with fumarate as an electron acceptor, even when fumarate-grown cells were exposed to oxygen, and Fe(III)-grown cells were grown anaerobically. These results suggest that the apparently high Geobacter cydA and sodA expression during bioremediation cannot necessarily be attributed to oxidative stress and demonstrate that diagnosis of the metabolic status of subsurface microorganisms through transcript analysis should be coupled with appropriate geochemical analyses.

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Avoiding high-valent iron intermediates: Superoxide reductase and rubrerythrin

Cited by 89 publications

References 145 publications

Nitrogen fixation in a chemoautotrophic lucinid symbiosis

Nitrogen fixation in a chemoautotrophic lucinid symbiosis

Intermolecular electron transfer in two-iron superoxide reductase: a putative role for the desulforedoxin center as an electron donor to the iron active site

Quantifying expression of Geobacter spp. oxidative stress genes in pure culture and during in situ uranium bioremediation

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