OmcB, a<i>c</i>-Type Polyheme Cytochrome, Involved in Fe(III) Reduction in<i>Geobacter sulfurreducens</i>

Leang, Ching; Coppi, Maddalena V.; Lovley, Derek R.

doi:10.1128/jb.185.7.2096-2103.2003

Cited by 306 publications

(315 citation statements)

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“…Gene deletion studies in G. sulfurreducens have shown that OmcB is critical for electron transfer to Fe(III) (Leang et al, 2003;Leang and Lovley, 2005) and that its expression can be directly linked to rates of Fe(III) reduction (Chin et al, 2004). Another gene that was upregulated in sediment-grown cells was the homolog of omcG, which encodes an outer-membrane c-type cytochrome in G. sulfurreducens that plays an important role in the proper expression of omcB (Kim et al, 2006).…”

Section: Resultsmentioning

confidence: 99%

“…Some of the cytochromes embedded in the outer membrane, such as OmcB (Qian et al, 2007), may also be important for extracellular electron transfer (Leang et al, 2003;Leang and Lovley, 2005), whereas others, such as OmcF, OmcG and OmcH, appear to participate in Fe(III) reduction indirectly by influencing the expression of other outer-surface cytochromes (Kim et al, 2005(Kim et al, , 2006. Studies have also suggested that some of the periplasmic and inner-membrane c-type cytochromes are involved in the transfer of electrons derived from central metabolism to the outer membrane .…”

Section: Resultsmentioning

confidence: 99%

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Transcriptome of Geobacter uraniireducens growing in uranium-contaminated subsurface sediments

et al. 2008

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To learn more about the physiological state of Geobacter species living in subsurface sediments, heat-sterilized sediments from a uranium-contaminated aquifer in Rifle, Colorado, were inoculated with Geobacter uraniireducens, a pure culture representative of the Geobacter species that predominates during in situ uranium bioremediation at this site. Whole-genome microarray analysis comparing sediment-grown G. uraniireducens with cells grown in defined culture medium indicated that there were 1084 genes that had higher transcript levels during growth in sediments. Thirty-four c-type cytochrome genes were upregulated in the sediment-grown cells, including several genes that are homologous to cytochromes that are required for optimal Fe(III) and U(VI) reduction by G. sulfurreducens. Sediment-grown cells also had higher levels of transcripts, indicative of such physiological states as nitrogen limitation, phosphate limitation and heavy metal stress. Quantitative reverse transcription PCR showed that many of the metabolic indicator genes that appeared to be upregulated in sediment-grown G. uraniireducens also showed an increase in expression in the natural community of Geobacter species present during an in situ uranium bioremediation field experiment at the Rifle site. These results demonstrate that it is feasible to monitor gene expression of a microorganism growing in sediments on a genome scale and that analysis of the physiological status of a pure culture growing in subsurface sediments can provide insights into the factors controlling the physiology of natural subsurface communities.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Transcriptome of Geobacter uraniireducens growing in uranium-contaminated subsurface sediments

et al. 2008

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“…Intact-cell and spheroplast suspensions were prepared in parallel from two 500 ml aliquots derived from a single, mid-exponential, acetate : fumarate (15 mM : 40 mM) culture. Intact-cell suspensions were prepared as previously described Leang et al, 2003). Because previously published methods for the production of G. sulfurreducens spheroplasts (Galushko & Schink, 2000;Kaufmann & Lovley, 2001) failed to yield homogeneous spheroplast preparations reproducibly, the spheroplast preparation protocol of Witholt et al (1976) was adapted for use in G. sulfurreducens.…”

Section: Methodsmentioning

confidence: 99%

“…In contrast, the subcellular localization of the reduction of chelated forms of Fe(III) is not known. Genetic studies conducted in G. sulfurreducens have implicated several periplasmic and outer-membrane cytochromes in Fe(III) citrate reduction (Butler et al, 2004;Kim et al, 2005Kim et al, , 2006Leang et al, 2003;Lloyd et al, 2003), suggesting that the reduction of Fe(III) citrate might occur at the cell surface. Biochemical studies performed in G. sulfurreducens have provided conflicting information regarding the site of Fe(III) chelate reduction.…”

Section: Introductionmentioning

confidence: 99%

“…Due to technical considerations, chelated forms of Fe(III), most often Fe(III) citrate and Fe(III) chelated with nitrilotriacetic acid (Fe(III)-NTA), are frequently used for laboratory studies addressing Fe(III) reduction by Geobacter species (Butler et al, 2004;Ding et al, 2006;Esteve-Nú ñez et al, 2005;Kim et al, 2005Kim et al, , 2006Leang et al, 2003;Lloyd et al, 2003;Methé et al, 2005;Nú ñez et al, 2004Nú ñez et al, , 2006). An understanding of the similarities and differences between the electron transport pathways to Fe(III) citrate and insoluble Fe(III) oxides is, therefore, crucial for determining the environmental relevance of these studies.…”

Section: Introductionmentioning

confidence: 99%

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Involvement of Geobacter sulfurreducens SfrAB in acetate metabolism rather than intracellular, respiration-linked Fe(III) citrate reduction

et al. 2007

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A soluble ferric reductase, SfrAB, which catalysed the NADPH-dependent reduction of chelated Fe(III), was previously purified from the dissimilatory Fe(III)-reducing micro-organism Geobacter sulfurreducens, suggesting that reduction of chelated forms of Fe(III) might be cytoplasmic. However, metabolically active spheroplast suspensions could not catalyse acetate-dependent Fe(III) citrate reduction, indicating that periplasmic and/or outer-membrane components were required for Fe(III) citrate reduction. Furthermore, phenotypic analysis of an SfrAB knockout mutant suggested that SfrAB was involved in acetate metabolism rather than respiration-linked Fe(III) reduction. The mutant could not grow via the reduction of either Fe(III) citrate or fumarate when acetate was the electron donor but could grow with either acceptor if either hydrogen or formate served as the electron donor. Following prolonged incubation in acetate : fumarate medium in the absence of hydrogen and formate, an 'acetate-adapted' SfrAB-null strain was isolated that was capable of growth on acetate : fumarate medium but not acetate : Fe(III) citrate medium. Comparison of gene expression in this strain with that of the wild-type revealed upregulation of a potential NADPH-dependent ferredoxin oxidoreductase as well as genes involved in energy generation and amino acid uptake, suggesting that NADPH homeostasis and the tricarboxylic acid (TCA) cycle were perturbed in the 'acetate-adapted' SfrAB-null strain. Membrane and soluble fractions prepared from the 'acetate-adapted' strain were depleted of NADPH-dependent Fe(III), viologen and quinone reductase activities. These results indicate that cytoplasmic, respiration-linked reduction of Fe(III) by SfrAB in vivo is unlikely and suggest that deleting SfrAB may interfere with growth via acetate oxidation by interfering with NADP regeneration.

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Multi‐Heme Cytochromes & Enzymes

Pereira

Xavier

2005

Encyclopedia of Inorganic Chemistry

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Multiheme c cytochromes and enzymes are a diverse group of proteins having several hemes c covalently bound to the polypeptide chain that are either enzymes involved in redox chemistry or electron transfer proteins. Most known members of this group are associated with the respiratory chains of proteobacteria. These proteins are characterized by a low amino acid to heme ratio, bis‐histidinyl coordination (with a few exceptions), and low redox potentials of the hemes. The hemes are usually tightly packed in close contact, allowing very fast electron transfer. Despite the absence of overall sequence identity between proteins, the hemes are found in quite conserved structural motifs, which tend to be organized in diheme pairs that are either parallel or perpendicular to each other. From the structures available, two families can be recognized in terms of the heme structural arrangement: the cytochrome c 3 family where the perpendicular motif is predominant, and the hydroxylamine oxidoreductase (HAO) family where the stacked parallel motif alternates with the perpendicular motifs. Other multiheme cytochromes for which the structure is not yet available may be part of novel structural families.

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OmcB, ac-Type Polyheme Cytochrome, Involved in Fe(III) Reduction inGeobacter sulfurreducens

Cited by 306 publications

References 56 publications

Transcriptome of Geobacter uraniireducens growing in uranium-contaminated subsurface sediments

Transcriptome of Geobacter uraniireducens growing in uranium-contaminated subsurface sediments

Involvement of Geobacter sulfurreducens SfrAB in acetate metabolism rather than intracellular, respiration-linked Fe(III) citrate reduction

Multi‐Heme Cytochromes & Enzymes

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