An essential role of the reversible electron-bifurcating hydrogenase Hnd for ethanol oxidation in Solidesulfovibrio fructosivorans

• Published in: Frontiers in microbiology Vol. 14; p. 1139276
• Main Authors: Kpebe, Arlette, Guendon, Chloé, Payne, Natalie, Ros, Julien, Khelil Berbar, Manel, Lebrun, Régine, Baffert, Carole, Shintu, Laetitia, Brugna, Myriam
• Format: Journal Article
• Language: English
• Published: Switzerland Frontiers Media 2023; Frontiers Media S.A
• Subjects: alcohol dehydrogenase; Bacteriology; Biochemistry; Biochemistry, Molecular Biology; Desulfovibrio; ethanol; Hnd; hydrogenase; Life Sciences; Microbiology; Microbiology and Parasitology; Solidesulfovibrio; Desulfovibrio; hydrogenase; Solidesulfovibrio; alcohol dehydrogenase; flavin-based electron bifurcation; ethanol; Hnd; aldehyde ferredoxin oxidoreductase
• ISSN: 1664-302X; 1664-302X
• DOI: 10.3389/fmicb.2023.1139276

The tetrameric cytoplasmic FeFe hydrogenase Hnd from
(formely
) catalyses H
oxidation and couples the exergonic reduction of NAD
to the endergonic reduction of a ferredoxin by using a flavin-based electron-bifurcating mechanism. Regarding its implication in the bacterial physiology, we previously showed that Hnd, which is non-essential when bacteria grow fermentatively on pyruvate, is involved in ethanol metabolism. Under these conditions, it consumes H
to produce reducing equivalents for ethanol production as a fermentative product. In this study, the approach implemented was to compare the two
WT and the
deletion mutant strains when grown on ethanol as the sole carbon and energy source. Based on the determination of bacterial growth, metabolite consumption and production, gene expression followed by RT-q-PCR, and Hnd protein level followed by mass spectrometry, our results confirm the role of Hnd hydrogenase in the ethanol metabolism and furthermore uncover for the first time an essential function for a
hydrogenase. Hnd is unequivocally required for
growth on ethanol, and we propose that it produces H
from NADH and reduced ferredoxin generated by an alcohol dehydrogenase and an aldehyde ferredoxin oxidoreductase catalyzing the conversion of ethanol into acetate. The produced H
could then be recycled and used for sulfate reduction. Hnd is thus a reversible hydrogenase that operates in H
-consumption by an electron-bifurcating mechanism during pyruvate fermentation and in H
-production by an electron-confurcating mechanism when the bacterium uses ethanol as electron donor.