Alignment of the
            <i>c</i>
            -Type Cytochrome OmcS along Pili of
            <i>Geobacter sulfurreducens</i>

Leang, Ching; Qian, Xinlei; Mester, Tünde; Lovley, Derek R.

doi:10.1128/aem.00023-10

Cited by 317 publications

(285 citation statements)

References 50 publications

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“…The pilT-2 gene (GSU0230), encoding one of the four putative pilus retraction ATPases of G. sulfurreducens, was upregulated on both Fe(III) oxide and Mn(IV) oxide (Table 2), and several other putative pilus biogenesis proteins were upregulated on Fe(III) oxide only (Table 3): pilL (GSU2039), pilY1-2 (GSU2038), fimU (GSU2037), pilV-2 (GSU2036) and pilM (GSU2032); or on Mn(IV) oxide only (Table 4): pilP (GSU2029) and pilQ (GSU2028). The upregulation of pilus biogenesis genes is consistent with the proposed route of electron transfer along pili to OmcS to Fe(III) and Mn(IV) oxides (Leang et al, 2010;.…”

Section: Methodssupporting

confidence: 83%

“…In Fe(III) oxide-grown cells, 28.3 times more omcS and 28.3 times more omcT transcripts were detected compared with Fe(III) citrategrown cells; in Mn(IV) oxide-grown cells, levels of omcS and omcT transcripts were 13.8-fold and 52.2-fold higher, respectively ( Table 1). As noted in the Introduction, previous studies have suggested that OmcS, which is localized along the pili (Leang et al, 2010), is the terminal Fe(III) and Mn(IV) reductase (Mehta et al, 2005;Qian et al, 2011). Despite high levels of expression of omcT, OmcT has been reported to be not abundant in the proteome of Fe(III) oxide-grown cells (Ding et al, 2008).…”

Section: Methodsmentioning

confidence: 99%

“…OmcS is localized on the type IV pili of G. sulfurreducens (Leang et al, 2010) that have been shown to exhibit a metal-like conductivity similar to that of organic conducting polymers (Malvankar & Lovley, 2012;Malvankar et al, 2011;Reguera et al, 2005). It has been postulated that electrons move away from the cell via these conductive pili to OmcS, which then facilitates electron transfer to Fe(III) oxide.…”

Section: Introductionmentioning

confidence: 99%

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Proteins involved in electron transfer to Fe(III) and Mn(IV) oxides by Geobacter sulfurreducens and Geobacter uraniireducens

et al. 2013

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Section: Methodssupporting

confidence: 83%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Proteins involved in electron transfer to Fe(III) and Mn(IV) oxides by Geobacter sulfurreducens and Geobacter uraniireducens

et al. 2013

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“…Such biofilms are electrically conductive, inferred by the ability of cells not in direct contact with the anode surface to contribute to current generation (22), and confirmed by two-electrode conductivity measurements (20,23). Geobacter cells possess an abundance of multiheme c-type cytochromes on their outer membrane, in the ECM, and along PilApili (24)(25)(26)(27)(28)(29)(30)(31)(32)(33). Cyclic voltammetry (19,(34)(35)(36)(37) and spectroelectrochemical measurements (38)(39)(40)(41)(42)(43) of actively respiring Geobacter biofilms are consistent with long-range electron transport mediated by sequential electron transfer reactions through a network of bound redox cofactors comprised of ECM c-type cytochromes terminating with electron transfer to the anode surface.…”

mentioning

confidence: 83%

Long-range electron transport in Geobacter sulfurreducens biofilms is redox gradient-driven

Snider

Glaven

Tsoi

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

246

210

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Geobacter spp. can acquire energy by coupling intracellular oxidation of organic matter with extracellular electron transfer to an anode (an electrode poised at a metabolically oxidizing potential), forming a biofilm extending many cell lengths away from the anode surface. It has been proposed that long-range electron transport in such biofilms occurs through a network of bound redox cofactors, thought to involve extracellular matrix c-type cytochromes, as occurs for polymers containing discrete redox moieties. Here, we report measurements of electron transport in actively respiring Geobacter sulfurreducens wild type biofilms using interdigitated microelectrode arrays. Measurements when one electrode is used as an anode and the other electrode is used to monitor redox status of the biofilm 15 μm away indicate the presence of an intrabiofilm redox gradient, in which the concentration of electrons residing within the proposed redox cofactor network is higher farther from the anode surface. The magnitude of the redox gradient seems to correlate with current, which is consistent with electron transport from cells in the biofilm to the anode, where electrons effectively diffuse from areas of high to low concentration, hopping between redox cofactors. Comparison with gate measurements, when one electrode is used as an electron source and the other electrode is used as an electron drain, suggests that there are multiple types of redox cofactors in Geobacter biofilms spanning a range in oxidation potential that can engage in electron transport. The majority of these redox cofactors, however, seem to have oxidation potentials too negative to be involved in electron transport when acetate is the electron source.microbial fuel cell | bioelectrochemical system | microbial electrochemistry | geomicrobiology | multistep electron hopping

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“…S4), which suggests that outer membrane c-cytochromes also contribute to the extracellular reduction of U(VI). It is unlikely that the outer membrane c-cytochrome OmcS, which has been hypothesized to mediate electron transfer between the conductive pili and metals (22), contributed to the pili-mediated reduction of U, because the pRG5::pilA strain expressed OmcS at wild-type levels (Fig. S5) yet reduced more U than the WT P+ (Fig.…”

mentioning

confidence: 99%

Extracellular reduction of uranium via Geobacter conductive pili as a protective cellular mechanism

Cologgi

Lampa-Pastirk

Speers

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

221

239

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The in situ stimulation of Fe(III) oxide reduction by Geobacter bacteria leads to the concomitant precipitation of hexavalent uranium [U(VI)] from groundwater. Despite its promise for the bioremediation of uranium contaminants, the biological mechanism behind this reaction remains elusive. Because Fe(III) oxide reduction requires the expression of Geobacter 's conductive pili, we evaluated their contribution to uranium reduction in Geobacter sulfurreducens grown under pili-inducing or noninducing conditions. A pilin-deficient mutant and a genetically complemented strain with reduced outer membrane c -cytochrome content were used as controls. Pili expression significantly enhanced the rate and extent of uranium immobilization per cell and prevented periplasmic mineralization. As a result, pili expression also preserved the vital respiratory activities of the cell envelope and the cell's viability. Uranium preferentially precipitated along the pili and, to a lesser extent, on outer membrane redox-active foci. In contrast, the pilus-defective strains had different degrees of periplasmic mineralization matching well with their outer membrane c -cytochrome content. X-ray absorption spectroscopy analyses demonstrated the extracellular reduction of U(VI) by the pili to mononuclear tetravalent uranium U(IV) complexed by carbon-containing ligands, consistent with a biological reduction. In contrast, the U(IV) in the pilin-deficient mutant cells also required an additional phosphorous ligand, in agreement with the predominantly periplasmic mineralization of uranium observed in this strain. These findings demonstrate a previously unrecognized role for Geobacter conductive pili in the extracellular reduction of uranium, and highlight its essential function as a catalytic and protective cellular mechanism that is of interest for the bioremediation of uranium-contaminated groundwater.

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Alignment of the c -Type Cytochrome OmcS along Pili of Geobacter sulfurreducens

Cited by 317 publications

References 50 publications

Proteins involved in electron transfer to Fe(III) and Mn(IV) oxides by Geobacter sulfurreducens and Geobacter uraniireducens

Proteins involved in electron transfer to Fe(III) and Mn(IV) oxides by Geobacter sulfurreducens and Geobacter uraniireducens

Long-range electron transport in Geobacter sulfurreducens biofilms is redox gradient-driven

Extracellular reduction of uranium via Geobacter conductive pili as a protective cellular mechanism

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