Identification of electron transfer enzymes in .

UNLABELLED

is a promising candidate for the production of biofuels from lignocellulosic sugars; however, the genes associated with electron transfer from ferredoxin are poorly characterized. In this work, we deleted several key electron transfer genes. We showed that the gene is not necessary for high-yield ethanol production, but that a set of four other genes (, , , and ) are necessary. We showed that the gene can function as a monofunctional (i.e., non-bifurcating) FNOR enzyme in the absence of . The phenotypes of the , , and double-deletion strains are consistent with their function via hydrogen cycling.

IMPORTANCE

The improved understanding of electron transfer pathways in will enable future efforts to transfer the robust ethanol production pathway from this microbe to other organisms, with potential implications for industrial biofuel production.