Characterization of a Novel Porin-Like Protein, ExtI, from Geobacter sulfurreducens and Its Implication in the Reduction of Selenite and Tellurite

Jahan, Mst Ishrat; Tobe, Ryuta; Mihara, Hisaaki

doi:10.3390/ijms19030809

Cited by 16 publications

(10 citation statements)

References 96 publications

(160 reference statements)

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“…In this regard, NADPH-dependent reduction activity toward high concentrations (5 mM) of SeO 3 2− was found in the cytoplasmic and, to a minor extent, in the periplasmic fractions of MPV1 cells [26]. SeO 3 2− bioprocessing can also be mediated by intracellular SeO 3 2− reductases [34,38], lignin peroxidase [39], chromate (CrsF), ferric (FerB) and arsenate reductases (ArsH) [37], or the metalloid-selective channel porin ExtI [40]. Thus, enzymatic systems might be accountable for the bioconversion of high oxyanion concentrations in MPV1, whereas low amounts of SeO 3 2− are likely bioprocessed through Painter-type reactions.…”

Section: Discussionmentioning

confidence: 99%

Influence of Bacterial Physiology on Processing of Selenite, Biogenesis of Nanomaterials and Their Thermodynamic Stability

et al. 2019

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We explored how Ochrobactrum sp. MPV1 can convert up to 2.5 mM selenite within 120 h, surviving the challenge posed by high oxyanion concentrations. The data show that thiol-based biotic chemical reaction(s) occur upon bacterial exposure to low selenite concentrations, whereas enzymatic systems account for oxyanion removal when 2 mM oxyanion is exceeded. The selenite bioprocessing produces selenium nanomaterials, whose size and morphology depend on the bacterial physiology. Selenium nanoparticles were always produced by MPV1 cells, featuring an average diameter ranging between 90 and 140 nm, which we conclude constitutes the thermodynamic stability range for these nanostructures. Alternatively, selenium nanorods were observed for bacterial cells exposed to high selenite concentration or under controlled metabolism. Biogenic nanomaterials were enclosed by an organic material in part composed of amphiphilic biomolecules, which could form nanosized structures independently. Bacterial physiology influences the surface charge characterizing the organic material, suggesting its diverse biomolecular composition and its involvement in the tuning of the nanomaterial morphology. Finally, the organic material is in thermodynamic equilibrium with nanomaterials and responsible for their electrosteric stabilization, as changes in the temperature slightly influence the stability of biogenic compared to chemogenic nanomaterials.

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Section: Discussionmentioning

confidence: 99%

Influence of Bacterial Physiology on Processing of Selenite, Biogenesis of Nanomaterials and Their Thermodynamic Stability

et al. 2019

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“…Rhodanase-like proteins related to ExtH typically are involved in sulfur metabolism ( 75 – 77 ), and an outer surface ExtH/rhodanese-like protein is linked to extracellular oxidation of metal sulfides by Acidithiobacillus ferrooxidans ( 78 ). Deletion of extI in G. sulfurreducens causes a severe defect in selenite and tellurite reduction ( 79 ). These links to metabolism of hydrogen, sulfur, and other oxyanions suggest roles outside metal reduction, and future genomic searches for electron conduit clusters should consider the possibility of noncytochrome components, such as FeS clusters, as the exposed lipoprotein.…”

Section: Discussionmentioning

confidence: 99%

Identification of Different Putative Outer Membrane Electron Conduits Necessary for Fe(III) Citrate, Fe(III) Oxide, Mn(IV) Oxide, or Electrode Reduction by Geobacter sulfurreducens

2018

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Gram-negative metal-reducing bacteria utilize electron conduits, chains of redox proteins spanning the outer membrane, to transfer electrons to the extracellular surface. Only one pathway for electron transfer across the outer membrane of Geobacter sulfurreducens has been linked to Fe(III) reduction. However, G. sulfurreducens is able to respire a wide array of extracellular substrates. Here we present the first combinatorial genetic analysis of five different electron conduits via creation of new markerless deletion strains and complementation vectors. Multiple conduit gene clusters appear to have overlapping roles, including two that have never been linked to metal reduction. Another recently described cluster (ExtABCD) was the only electron conduit essential during electrode reduction, a substrate of special importance to biotechnological applications of this organism.

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“…Rhodanase-like proteins related to ExtH typically are involved in sulfur metabolism (75)(76)(77), and an outer surface ExtH/rhodanese-like protein is linked to extracellular oxidation of metal sulfides by Acidithiobacillus ferrooxidans (78). Deletion of extI in G. sulfurreducens causes a severe defect in selenite and tellurite reduction (79). These links to metabolism of hydrogen, sulfur, and other oxyanions suggest roles outside metal reduction, and future genomic searches for electron conduit clusters should consider the possibility of noncytochrome components, such as FeS clusters, as the exposed lipoprotein.…”

Section: Discussionmentioning

confidence: 99%

Identification of different putative outer membrane electron conduits necessary for Fe(III) citrate, Fe(III)-oxide, Mn(IV)-oxide, or electrode reduction by Geobacter sulfurreducens .

Otero¹,

Chan²,

Bond³

2018

Preprint

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At least five gene clusters in the Geobacter sulfurreducens genome encode putative ‘electron conduits’ implicated in electron transfer across the outer membrane, each containing a periplasmic multiheme c -type cytochrome, integral outer membrane anchor, and outer membrane redox lipoprotein(s). Markerless single gene cluster deletions and all possible multiple deletion combinations were constructed and grown with soluble Fe(III) citrate, Fe(III)- and Mn(IV)-oxides, and graphite electrodes poised at +0.24 V and -0.1 V vs. SHE. Different gene clusters were necessary for reduction of each electron acceptor. During metal oxide reduction, deletion of the previously described omcBC cluster caused defects, but deletion of additional components in an Δ omcBC background, such as extEFG , were needed to produce defects greater than 50% compared to wild type. Deletion of all five gene clusters abolished all metal reduction. During electrode reduction, only the Δ extABCD mutant had a severe growth defect at both redox potentials, while this mutation did not affect Fe(III)-oxide, Mn(IV)-oxide, or Fe(III) citrate reduction. Some mutants containing only one cluster were able to reduce particular terminal electron acceptors better than wild type, suggesting routes for improvement by targeting specific electron transfer pathways. Transcriptomic comparisons between fumarate and electrode-based growth showed all of these ext clusters to be constitutive, and transcriptional analysis of the triple-deletion strain containing only extABCD detected no significant changes in expression of known redox proteins or pili components. These genetic experiments reveal new outer membrane conduit complexes necessary for growth of G. sulfurreducens , depending on the available extracellular electron acceptor.

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Characterization of a Novel Porin-Like Protein, ExtI, from Geobacter sulfurreducens and Its Implication in the Reduction of Selenite and Tellurite

Cited by 16 publications

References 96 publications

Influence of Bacterial Physiology on Processing of Selenite, Biogenesis of Nanomaterials and Their Thermodynamic Stability

Influence of Bacterial Physiology on Processing of Selenite, Biogenesis of Nanomaterials and Their Thermodynamic Stability

Identification of Different Putative Outer Membrane Electron Conduits Necessary for Fe(III) Citrate, Fe(III) Oxide, Mn(IV) Oxide, or Electrode Reduction by Geobacter sulfurreducens

Identification of different putative outer membrane electron conduits necessary for Fe(III) citrate, Fe(III)-oxide, Mn(IV)-oxide, or electrode reduction by Geobacter sulfurreducens .

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