Energy conservation via hydrogen cycling in the methanogenic archaeon<i>Methanosarcina barkeri</i>

Kulkarni, Gargi; Mand, Thomas D.; Metcalf, William W.

doi:10.1101/335794

Cited by 2 publications

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“…More recent models propose that two electron transfer routes from lactate to sulfate operate simultaneously: the pathway of the hydrogen cycling model including the transient production and consumption of H 2 , and a second H 2independent pathway involving a direct electron transfer from the donor to the acceptor ( Figure 2) (Keller & Wall, 2011;Noguera, Brusseau, Rittmann, & Stahl, 1998;Sim et al, 2013). In the methanogenic archaeon Methanosarcina barkeri, Kulkarni et al have very recently demonstrated, thanks to a series of hydrogenase mutants, the role of H 2 cycling in energy conservation and proposed, based on the common occurrence of both cytoplasmic and periplasmic hydrogenases, that this mechanism may be widespread in nature, especially among anaerobic microorganisms (Kulkarni, Mand, & Metcalf, 2018).…”

Section: Different Models For the H 2 Metabolismmentioning

confidence: 99%

“…This endergonic reduction is driven by the electrochemical proton potential (Forzi et al, 2005;Hedderich, 2004) ( Figure 5B). It has recently been demonstrated that Methanosarcina barkeri is capable of energy conservation via H 2 -cycling thanks to two H 2 -producing cytoplasmic hydrogenases, among them is Ech, and a H 2oxidizing periplasmic hydrogenase (Kulkarni et al, 2018). In Thermoanaerobacter tengcongensis (now Caldanaerobacter subterraneus subsp.…”

Section: The Ech Hydrogenasementioning

confidence: 99%

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Hydrogenases and H2 metabolism in sulfate-reducing bacteria of the Desulfovibrio genus

Baffert

Kpebe

Avilán

et al. 2019

Advances in Microbial Physiology

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Hydrogen metabolism plays a central role in sulfate-reducing bacteria of the Desulfovibrio genus and is based on hydrogenases that catalyze the reversible conversion of protons into dihydrogen. These metabolically versatile microorganisms possess a complex hydrogenase system composed of several enzymes of both [FeFe]-and [NiFe]-type that can vary considerably from one Desulfovibrio species to another. This review covers the molecular and physiological aspects of hydrogenases and H 2 metabolism in Desulfovibrio but focuses particularly on our model bacterium Desulfovibrio fructosovorans. The search of hydrogenase genes in more than 30 sequenced genomes provides an overview of the distribution of these enzymes in Desulfovibrio. Our discussion will consider the significance of the involvement of electron-bifurcation in H 2 metabolism.

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Section: Different Models For the H 2 Metabolismmentioning

confidence: 99%

Section: The Ech Hydrogenasementioning

confidence: 99%

Hydrogenases and H2 metabolism in sulfate-reducing bacteria of the Desulfovibrio genus

Baffert

Kpebe

Avilán

et al. 2019

Advances in Microbial Physiology

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Genetic, biochemical, and molecular characterization ofMethanosarcina barkerimutants lacking three distinct classes of hydrogenase

Mand

Kulkarni

Metcalf

2018

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17The methanogenic archaeon Methanosarcina barkeri encodes three distinct 18 types of hydrogenase, whose functions vary depending on the growth substrate. 19These include the F420-dependent (Frh), methanophenazine-dependent (Vht), and 20 ferredoxin-dependent (Ech) hydrogenases. To investigate their physiological roles, 21we characterized a series of mutants lacking each hydrogenase in various 22 40 IMPORTANCE 41Methanogenic archaea are key players in the global carbon cycle due to their 42 ability to facilitate the remineralization of organic substrates in many anaerobic 43 environments. The consequences of biological methanogenesis are far reaching, 44 with impacts on atmospheric methane and CO2 concentrations, agriculture, energy 45 production, waste treatment and human health. The data presented here clarify the 46 in vivo function of hydrogenases during methanogenesis, which in turn deepens our 47 understanding of this unique form of metabolism. This knowledge is critical for a 48 variety of important issues ranging from atmospheric composition to human health. 49 50 Methanogens without cytochromes produce at least four types of 62 hydrogenase; including (i) the electron-bifurcating Mvh hydrogenase, which couples 63 oxidation of hydrogen to reduction of ferredoxin and a mixed coenzyme M-64 coenzyme B disulfide, (ii) the coenzyme F420-dependent hydrogenase, (iii) the [Fe] 65 hydrogenase, which couples hydrogen oxidation to reduction of 66 methenyltetrahydromethanopterin, and (iv) the ferredoxin-dependent, energy-67 converting hydrogenases (4). The first three are cytoplasmic enzymes, which supply 68 the electrons needed to reduce CO2 to methane. The last is a membrane bound 69 multi-subunit complex that couples hydrogenase activity to the 70 production/consumption of the ion-motive force across the cell membrane (hence 71 the designation as "energy-converting"). In non-cytochrome-containing 72 methanogens, these energy-converting hydrogenases are believed to provide low-73 potential electrons, in the form of reduced ferredoxin, needed for anaplerotic 74 reactions (6). 75Methanogens with cytochromes, typified by Methanosarcina barkeri, encode 76 a different set of hydrogenases that includes one cytoplasmic and two membrane-77 bound enzymes (Fig 1) (7). Like the non-cytochrome containing methanogens, M. 78 barkeri produces a cytoplasmic, three-subunit F420-dependent hydrogenase known 79 as Frh (for F420-reducing hydrogenase). Frh is encoded by the four-gene frhADGB 80 operon, which encodes the α, β and γ subunits (FrhA, FrhB and FrhG, respectively), 81 along with the maturation protease FrhD (8). A second locus, freAEGB, encodes 82 proteins that are 86-88% identical to FrhA, FrhB and FrhG, but lacks the gene for the 83 maturation protease FrhD, instead encoding a small protein of unknown function 84 (FrhE). It is not known whether the fre operon is capable of producing an active 85 hydrogenase (8)(9)(10)(11). A membrane-bound hydrogenase linked to the quinone-like 86 electron carrier methanophenazine has, to dat...

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Energy conservation via hydrogen cycling in the methanogenic archaeonMethanosarcina barkeri

Abstract: word count: 208 16Importance word count: 88 17 Main text word count: 3579 18 19All rights reserved. No reuse allowed without permission.(which was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.

Cited by 2 publications

References 52 publications

Hydrogenases and H2 metabolism in sulfate-reducing bacteria of the Desulfovibrio genus

Hydrogenases and H2 metabolism in sulfate-reducing bacteria of the Desulfovibrio genus

Genetic, biochemical, and molecular characterization ofMethanosarcina barkerimutants lacking three distinct classes of hydrogenase

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