Abstract
BackgroundRuminants burp massive amounts of methane into the atmosphere and significantly contribute to the deposition of greenhouse gases and the consequent global warming. It is therefore urgent to devise strategies to mitigate ruminant’s methane emissions to alleviate climate change. Ruminal methanogenesis is accomplished by a series of methanogen archaea in the phylum Euryarchaeota, which piggyback into carbohydrate fermentation by utilizing residual hydrogen to produce methane. Abundance of methanogens, therefore, is expected to affect methane production. Furthermore, availability of hydrogen produced by cellulolytic bacteria acting upstream of methanogens is a rate-limiting factor for methane production. The aim of our study was to identify microbes associated with the production of methane which would constitute the basis for the design of mitigation strategies.ResultsModerate differences in the abundance of methanogens were observed between groups. In addition, we present three lines of evidence suggesting an apparent higher abundance of a consortium of Prevotella species in animals with lower methane emissions. First, taxonomic classification revealed increased abundance of at least 29 species of Prevotella. Second, metagenome assembly identified increased abundance of Prevotella ruminicola and another species of Prevotella. Third, metabolic profiling of predicted proteins uncovered 25 enzymes with homology to Prevotella proteins more abundant in the low methane emissions group.ConclusionsWe propose that higher abundance of ruminal Prevotella increases the production of propionic acid and, in doing so, reduces the amount of hydrogen available for methanogenesis. However, further experimentation is required to ascertain the role of Prevotella on methane production and its potential to act as a methane production mitigator.
Highlights
Ruminants burp massive amounts of methane into the atmosphere and significantly contribute to the deposition of greenhouse gases and the consequent global warming
With the advent of generation sequencing (NGS), the microbiome of ruminants is being profiled at high resolution and throughput and a complex picture is emerging wherein host genetics and microbiome structure additively contribute to several phenotypes, including methane emissions [13]
Alignment of individual sequences Taxonomic classification of sequences was performed using the software Kraken2 [19], and the standard database complemented with all bacterial, fungal, viral and archaeal sequences in the GenBank plus all sequences deposited in the Genome taxonomy database, Genome Taxonomy Database (GTDB)
Summary
Ruminants burp massive amounts of methane into the atmosphere and significantly contribute to the deposition of greenhouse gases and the consequent global warming. Ruminal methanogenesis is accomplished by a series of methanogen archaea in the phylum Euryarchaeota, which piggyback into carbohydrate fermentation by utilizing residual hydrogen to produce methane. The aim of our study was to identify microbes associated with the production of methane which would constitute the basis for the design of mitigation strategies. Methane is produced during enteric fermentation in ruminants by anaerobic microorganisms collectively known as methanogens in the Archaea domain and the phylum Euryarchaeota [7]. Methanogenesis is considered an essential process for ruminants because if hydrogen generated during carbohydrate fermentation is not removed, it may inhibit microbiome metabolism [7]. Finding ways to redirect hydrogen metabolism is a promising avenue to mitigate methane emissions and to improve energy retention from grazing [10]
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