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Publication Details
AFRICAN RESEARCH NEXUS
SHINING A SPOTLIGHT ON AFRICAN RESEARCH
agricultural and biological sciences
Diverse hydrogen production and consumption pathways influence methane production in ruminants
ISME Journal, Volume 13, No. 10, Year 2019
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Description
Farmed ruminants are the largest source of anthropogenic methane emissions globally. The methanogenic archaea responsible for these emissions use molecular hydrogen (H2), produced during bacterial and eukaryotic carbohydrate fermentation, as their primary energy source. In this work, we used comparative genomic, metatranscriptomic and co-culture-based approaches to gain a system-wide understanding of the organisms and pathways responsible for ruminal H2 metabolism. Two-thirds of sequenced rumen bacterial and archaeal genomes encode enzymes that catalyse H2 production or consumption, including 26 distinct hydrogenase subgroups. Metatranscriptomic analysis confirmed that these hydrogenases are differentially expressed in sheep rumen. Electron-bifurcating [FeFe]-hydrogenases from carbohydrate-fermenting Clostridia (e.g., Ruminococcus) accounted for half of all hydrogenase transcripts. Various H2 uptake pathways were also expressed, including methanogenesis (Methanobrevibacter), fumarate and nitrite reduction (Selenomonas), and acetogenesis (Blautia). Whereas methanogenesis-related transcripts predominated in high methane yield sheep, alternative uptake pathways were significantly upregulated in low methane yield sheep. Complementing these findings, we observed significant differential expression and activity of the hydrogenases of the hydrogenogenic cellulose fermenter Ruminococcus albus and the hydrogenotrophic fumarate reducer Wolinella succinogenes in co-culture compared with pure culture. We conclude that H2 metabolism is a more complex and widespread trait among rumen microorganisms than previously recognised. There is evidence that alternative hydrogenotrophs, including acetogenic and respiratory bacteria, can prosper in the rumen and effectively compete with methanogens for H2. These findings may help to inform ongoing strategies to mitigate methane emissions by increasing flux through alternative H2 uptake pathways, including through animal selection, dietary supplementation and methanogenesis inhibitors. © 2019, The Author(s).
Authors & Co-Authors
Greening, Chris
Australia, Clayton
Monash University
Koike, Satoshi
Japan, Sapporo
Hokkaido University
Leahy, Sinead C.
New Zealand, Palmerston North
Agresearch Grasslands
Kelly, William J.
Unknown Affiliation
Cann, Isaac K.O.
United States, Urbana
University of Illinois Urbana-champaign
Cook, Gregory M.
New Zealand, Dunedin
University of Otago
Mackie, Roderick Ian
United States, Urbana
University of Illinois Urbana-champaign
Statistics
Citations: 108
Authors: 7
Affiliations: 5
Identifiers
Doi:
10.1038/s41396-019-0464-2
ISSN:
17517362