Two functionally distinct NADP-dependent ferredoxin oxidoreductases maintain the primary redox balance of .

Electron bifurcation has recently gained acceptance as the third mechanism of energy conservation in which energy is conserved through the coupling of exergonic and endergonic reactions. A structure-based mechanism of bifurcation has been elucidated recently for the flavin-based enzyme NADH-dependent ferredoxin NADP oxidoreductase I (NfnI) from the hyperthermophillic archaeon NfnI is thought to be involved in maintaining the cellular redox balance, producing NADPH for biosynthesis by recycling the two other primary redox carriers, NADH and ferredoxin. The genome encodes an NfnI paralog termed NfnII, and the two are differentially expressed, depending on the growth conditions.

Engineering hydrogen gas production from formate in a hyperthermophile by heterologous production of an 18-subunit membrane-bound complex.

Biohydrogen gas has enormous potential as a source of reductant for the microbial production of biofuels, but its low solubility and poor gas mass transfer rates are limiting factors. These limitations could be circumvented by engineering biofuel production in microorganisms that are also capable of generating H2 from highly soluble chemicals such as formate, which can function as an electron donor. Herein, the model hyperthermophile, Pyrococcus furiosus, which grows optimally near 100 °C by fermenting sugars to produce H2, has been engineered to also efficiently convert formate to H2.

Exploiting microbial hyperthermophilicity to produce an industrial chemical, using hydrogen and carbon dioxide.

Microorganisms can be engineered to produce useful products, including chemicals and fuels from sugars derived from renewable feedstocks, such as plant biomass. An alternative method is to use low potential reducing power from nonbiomass sources, such as hydrogen gas or electricity, to reduce carbon dioxide directly into products. This approach circumvents the overall low efficiency of photosynthesis and the production of sugar intermediates.

Mutational Analyses of the Enzymes Involved in the Metabolism of Hydrogen by the Hyperthermophilic Archaeon Pyrococcus furiosus.

Pyrococcus furiosus grows optimally near 100°C by fermenting carbohydrates to produce hydrogen (H(2)) or, if elemental sulfur (S(0)) is present, hydrogen sulfide instead. It contains two cytoplasmic hydrogenases, SHI and SHII, that use NADP(H) as an electron carrier and a membrane-bound hydrogenase (MBH) that utilizes the redox protein ferredoxin. We previously constructed deletion strains lacking SHI and/or SHII and showed that they exhibited no obvious phenotype.