title: Deletion of a gene cluster for [Ni-Fe] hydrogenase maturation in the anaerobic hyperthermophilic bacterium Caldicellulosiruptor bescii identifies its role in hydrogen metabolism.
abstract: The anaerobic, hyperthermophlic, cellulolytic bacterium Caldicellulosiruptor bescii grows optimally at ∼80 °C and effectively degrades plant biomass without conventional pretreatment. It utilizes a variety of carbohydrate carbon sources, including both C5 and C6 sugars, released from plant biomass and produces lactate, acetate, CO2, and H2 as primary fermentation products. The C. bescii genome encodes two hydrogenases, a bifurcating [Fe-Fe] hydrogenase and a [Ni-Fe] hydrogenase. The [Ni-Fe] hydrogenase is the most widely distributed in nature and is predicted to catalyze hydrogen production and to pump protons across the cellular membrane creating proton motive force. Hydrogenases are the key enzymes in hydrogen metabolism and their crystal structure reveals complexity in the organization of their prosthetic groups suggesting extensive maturation of the primary protein. Here, we report the deletion of a cluster of genes, hypABFCDE, required for maturation of the [Ni-Fe] hydrogenase. These proteins are specific for the hydrogenases they modify and are required for hydrogenase activity. The deletion strain grew more slowly than the wild type or the parent strain and produced slightly less hydrogen overall, but more hydrogen per mole of cellobiose. Acetate yield per mole of cellobiose was increased ∼67 % and ethanol yield per mole of cellobiose was decreased ∼39 %. These data suggest that the primary role of the [Ni-Fe] hydrogenase is to generate a proton gradient in the membrane driving ATP synthesis and is not the primary enzyme for hydrogen catalysis. In its absence, ATP is generated from increased acetate production resulting in more hydrogen produced per mole of cellobiose.
authors.affiliation: Department of Genetics, University of Georgia, Athens, GA, 30602, USA.|The BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA.
authors.forename: Minseok
authors.initials: M
authors.lastname: Cha
authors.affiliation: Department of Genetics, University of Georgia, Athens, GA, 30602, USA.|The BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA.
authors.forename: Daehwan
authors.initials: D
authors.lastname: Chung
authors.affiliation: Department of Genetics, University of Georgia, Athens, GA, 30602, USA. janwest@uga.edu.|The BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA. janwest@uga.edu.
authors.forename: Janet
authors.initials: J
authors.lastname: Westpheling
mesh_terms: D000085:Acetates / Q000378:metabolism; D002475:Cellobiose / Q000378:metabolism; D000431:Ethanol / Q000378:metabolism; D000068536:Bacillota / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D017353:Gene Deletion; D006859:Hydrogen / Q000378:metabolism*; D006864:Hydrogenase / Q000235:genetics / Q000378:metabolism*; D005810:Multigene Family; D011499:Protein Processing, Post-Translational
chemical_list: D000085:Acetates; D002475:Cellobiose; D000431:Ethanol; D006859:Hydrogen; C043296:nickel-iron hydrogenase; D006864:Hydrogenase
keywords: Anaerobe; Bifurcating [Fe-Fe] hydrogenase; Caldicellulosiruptor bescii; Hydrogen; Hydrogenase maturation proteins; Hyperthermophile; [Ni-Fe] hydrogenase