The Rnf Complex of Clostridium ljungdahlii Is a Proton-Translocating Ferredoxin:NAD
            <sup>+</sup>
            Oxidoreductase Essential for Autotrophic Growth

Tremblay, Pier-Luc; Zhang, Tian; Dar, Shabir Ahmad; Leang, Ching; Lovley, Derek R.

doi:10.1128/mbio.00406-12

Cited by 201 publications

(200 citation statements)

References 41 publications

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“…As for syntrophs who do not encode Rnf and Hdr-Ifo or ECHyd, this survey reveals other reverse electron transport and electron bi(con)furcation mechanisms that syntrophs may employ. For acetogenesis, we identify that acetogens require (Schmidt et al, 2009) and encode at least one energy-conserving electron transfer between physiological electron carriers (Rnf, NAD(P)H transhydrogenase and/or NADH-dependent Fd red :NADP þ oxidoreductase) (Hugenholtz and Ljungdahl, 1989;Muller et al, 2008;Huang et al, 2012;Tremblay et al, 2012); often possess a putative clostridial sensory hydrogenase (Calusinska et al, 2010); and utilize a wide variety of hydrogenases and formate dehydrogenases. In addition, we identify five genotypes of acetogen MetF (methylenetetrahydrofolate reductase) essential for driving the homoacetogenic Wood-Ljungdahl pathway, but also postulate that undiscovered MetF homologs and genotypes must exist.…”

Section: Metatranscriptomicsmentioning

confidence: 99%

Microbial dark matter ecogenomics reveals complex synergistic networks in a methanogenic bioreactor

et al. 2015

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Ecogenomic investigation of a methanogenic bioreactor degrading terephthalate (TA) allowed elucidation of complex synergistic networks of uncultivated microorganisms, including those from candidate phyla with no cultivated representatives. Our previous metagenomic investigation proposed that Pelotomaculum and methanogens may interact with uncultivated organisms to degrade TA; however, many members of the community remained unaddressed because of past technological limitations. In further pursuit, this study employed state-of-the-art omics tools to generate draft genomes and transcriptomes for uncultivated organisms spanning 15 phyla and reports the first genomic insight into candidate phyla Atribacteria, Hydrogenedentes and Marinimicrobia in methanogenic environments. Metabolic reconstruction revealed that these organisms perform fermentative, syntrophic and acetogenic catabolism facilitated by energy conservation revolving around H 2 metabolism. Several of these organisms could degrade TA catabolism by-products (acetate, butyrate and H 2 ) and syntrophically support Pelotomaculum. Other taxa could scavenge anabolic products (protein and lipids) presumably derived from detrital biomass produced by the TA-degrading community. The protein scavengers expressed complementary metabolic pathways indicating syntrophic and fermentative step-wise protein degradation through amino acids, branched-chain fatty acids and propionate. Thus, the uncultivated organisms may interact to form an intricate syntrophy-supported food web with Pelotomaculum and methanogens to metabolize catabolic by-products and detritus, whereby facilitating holistic TA mineralization to CO 2 and CH 4 .

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Section: Metatranscriptomicsmentioning

confidence: 99%

Microbial dark matter ecogenomics reveals complex synergistic networks in a methanogenic bioreactor

et al. 2015

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“…The reduction of ferredoxin well above its midpoint potential (E • = −420 mV) by H 2 drives the function of the Rnf complex, but the imposed mutation blocked the transfer of electrons from H 2 into the Rnf complex circuit, and without a supply of energy, the chemical potential across the membrane was dissipated. Presumably, autotrophic growth of the C. ljungdahlii mutant on CO would also have been blocked, although this was not reported by [68]. Insulation of the electron current by the cell membrane is critical to the function of the Rnf electron transfer chain that transports H + across the membrane and terminates in reduction of methylene-THF to methyl-THF.…”

Section: Energymentioning

confidence: 84%

“…A single crossover integration in C. ljungdahlii was reported to block the production of "a membrane associated polyferredoxin accepting electrons from ferredoxin and transferring them to membrane domains of the Rnf complex" [68]. Autotrophic growth on H 2 and CO 2 was blocked by this mutation, and the "proton gradient, membrane potential and protonmotive force collapsed".…”

Section: Energymentioning

confidence: 99%

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Syngas Fermentation: A Microbial Conversion Process of Gaseous Substrates to Various Products

2017

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Biomass and other carbonaceous materials can be gasified to produce syngas with high concentrations of CO and H 2 . Feedstock materials include wood, dedicated energy crops, grain wastes, manufacturing or municipal wastes, natural gas, petroleum and chemical wastes, lignin, coal and tires. Syngas fermentation converts CO and H 2 to alcohols and organic acids and uses concepts applicable in fermentation of gas phase substrates. The growth of chemoautotrophic microbes produces a wide range of chemicals from the enzyme platform of native organisms. In this review paper, the Wood-Ljungdahl biochemical pathway used by chemoautotrophs is described including balanced reactions, reaction sites physically located within the cell and cell mechanisms for energy conservation that govern production. Important concepts discussed include gas solubility, mass transfer, thermodynamics of enzyme-catalyzed reactions, electrochemistry and cellular electron carriers and fermentation kinetics. Potential applications of these concepts include acid and alcohol production, hydrogen generation and conversion of methane to liquids or hydrogen.

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“…No known electron-bifurcating complexes are present in the S. denitrificans genome (Marshall et al, 2012), nor is there evidence for complexes coupling endergonic ferredoxin reduction to the proton motive force (e.g. Tremblay et al, 2013).…”

Section: Reverse Electron Transportmentioning

confidence: 99%

Productivity, metabolism and physiology of free-living chemoautotrophic Epsilonproteobacteria

McNichol¹

2016

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Chemoautotrophic ecosystems at deep-sea hydrothermal vents were discovered in 1977, but not until 1995 were free-living autotrophic Epsilonproteobacteria identified as important microbial community members. Because the deep-sea is food-starved, the autotrophic metabolism of hydrothermal vent Epsilonproteobacteria may be very important for deep-sea consumers. However, quantifying their metabolic activities in situ has remained difficult, and biochemical mechanisms underlying their autotrophic physiology are poorly described. To gain insight into environmental processes, an approach was developed for incubations of microbes at in situ pressure and temperature (25 MPa, 24 o C) with various combinations of electron donors/acceptors (H 2 , O 2 and NO 3 -and 13 HCO 3 -) as a tracer to track carbon fixation. During short (18-24 h) incubations of low-temperature vent fluids from Crab Spa (9 o N East Pacific Rise), the concentration of electron donors/acceptors and cell numbers were monitored to quantify microbial processes. Measured rates were generally higher than previous studies, and the stoichiometry of microbially-catalyzed redox reactions revealed new insights into sulfur and nitrogen cycling. Single-cell, taxonomically-resolved tracer incorporation showed Epsilonproteobacteria dominated carbon fixation, and their growth efficiency was calculated based on electron acceptor consumption. Using these data, in situ primary productivity, microbial standing stock, and average biomass residence time of the deep-sea vent subseafloor biosphere were estimated. Finally, the population structures of the most abundant genera Sulfurimonas and Thioreductor were shown to be strongly influenced by pO 2 and temperature respectively, providing a mechanism for niche differentiation in situ. To gain insights into the core biochemical reactions underlying autotrophy in Epsilonprotebacteria, a theoretical metabolic model of Sulfurimonas denitrificans was developed. Validated iteratively by comparing in silico yields with data from chemostat experiments, the model generated hypotheses explaining critical, yet so far unresolved reactions supporting chemoautotrophy in Epsilonproteobacteria. For example, it provides insight into how energy is conserved during sulfur oxidation coupled to denitrification, how reverse electron transport produces ferredoxin for carbon fixation, and why aerobic growth yields are only slightly higher compared to denitrification. As a whole, this thesis provides important contributions towards understanding core mechanisms of chemoautrophy, as well as the in situ productivity, physiology and ecology of autotrophic Epsilonproteobacteria.

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The Rnf Complex of Clostridium ljungdahlii Is a Proton-Translocating Ferredoxin:NAD ⁺ Oxidoreductase Essential for Autotrophic Growth

Cited by 201 publications

References 41 publications

Microbial dark matter ecogenomics reveals complex synergistic networks in a methanogenic bioreactor

Microbial dark matter ecogenomics reveals complex synergistic networks in a methanogenic bioreactor

Syngas Fermentation: A Microbial Conversion Process of Gaseous Substrates to Various Products

Productivity, metabolism and physiology of free-living chemoautotrophic Epsilonproteobacteria

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The Rnf Complex of Clostridium ljungdahlii Is a Proton-Translocating Ferredoxin:NAD + Oxidoreductase Essential for Autotrophic Growth

Cited by 201 publications

References 41 publications

Microbial dark matter ecogenomics reveals complex synergistic networks in a methanogenic bioreactor

Microbial dark matter ecogenomics reveals complex synergistic networks in a methanogenic bioreactor

Syngas Fermentation: A Microbial Conversion Process of Gaseous Substrates to Various Products

Productivity, metabolism and physiology of free-living chemoautotrophic Epsilonproteobacteria

Contact Info

Product

Resources

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The Rnf Complex of Clostridium ljungdahlii Is a Proton-Translocating Ferredoxin:NAD ⁺ Oxidoreductase Essential for Autotrophic Growth