# Acetate-based syntrophy enhances methane production potential of ruminant feces

## TL;DR

This study shows that ruminant feces, like sheep, produce more methane mainly through the acetoclastic pathway, which involves a close partnership between bacteria and archaea.

## Contribution

The study identifies acetoclastic methanogenesis as a key pathway in ruminant feces and reveals a coordinated microbial partnership driving high methane production.

## Key findings

- Sheep feces have threefold higher methane production potential compared to non-ruminants.
- Acetoclastic methanogenesis is the dominant pathway in sheep feces, supported by higher abundance of related genes.
- A tight microbial partnership between acetogenic bacteria and methanogenic archaea is observed in sheep feces.

## Abstract

Livestock feces contribute to approximately 32% of global methane emissions. Although ruminants are generally believed to have a higher methane production potential than non-ruminants, the dominant pathways and key regulatory processes underlying methane generation in ruminants remain poorly understood, impeding effective manure management and accurate livestock emission assessments. In this study, metagenomic and carbon isotope techniques were employed to investigate methane production potential and key pathways in sheep, pig, chicken, and duck feces. Methane production potential of ruminant sheep feces was significantly higher (approximately threefold) compared to that of non-ruminants. Isotopic analysis of methane sources revealed that sheep feces primarily produce methane through the acetoclastic pathway, whereas the other three likely rely on CO2 reduction. Metagenomic analysis of methanogenic pathways further indicated that the abundance of functional genes associated with acetoclastic methanogenesis is significantly higher in sheep feces compared to the other three. Moreover, the co-occurrence network analysis highlighted a tightly coordinated, cross-species partnership between fermentative acetogenic bacteria and methanogenic archaea in the sheep fecal microbiome. Together, our findings provide insights into some key methanogenic pathways, such as acetoclastic methanogenesis, contributing to high methane production from ruminant feces.