Ruminant livestock contribute significantly to global food security by converting lignocellulosic plant biomass into high-quality animal protein. However, microbial fermentation in the rumen produces methane (CH₄), a potent greenhouse gas. This process not only contributes to global warming but also represents an energy loss for the host animal. Acetogenic bacteria offer a potential alternative hydrogen sink through the reductive Wood–Ljungdahl pathway, which incorporates electrons for acetate production as a usable energy source for the host. Yet, due to their lower affinity for H₂, acetogens are generally outcompeted by methanogens in the rumen. Understanding the coexistence strategies that enable the ubiquitous acetogens to potentially compete in this H₂-limited environment, is critical for developing approaches for methane mitigation, while enhancing ruminant energy efficiency and sustainability.
This study found that acetogens are phylogenetically diverse, widely distributed, and possess conserved genes for reductive acetogenesis through analyzing global metagenomes from ruminants. These acetogens exhibit metabolic versatility, using both molecular hydrogen and carbohydrates as electron donors, allowing them to persist alongside methanogens despite unfavorable thermodynamics. Validation through animal trials, in vitro fermentations, and DNA stable isotope probing confirmed active acetogenesis in the rumen of cattle. Notably, fiber-rich diets enriched heterotrophic acetogens, which shows the capacity to enhance acetate production and reduce methane emissions. These findings demonstrate that dietary modulation can enhance acetogen activity and offer a promising strategy to mitigate methane emissions while improving ruminant energy efficiency.
The findings advance current understanding of rumen microbial ecology by uncovering the phylogenetic and metabolic diversity of acetogens and demonstrating their selective enrichment in response to dietary carbohydrate type. The identification of heterotrophic acetogens capable of utilizing electrons from organic substrate fermentation, rather than H₂, reveals an underexplored electron sink that may function independently of direct competition with methanogens for H₂. These findings highlight the potential of targeting acetogenesis to mitigate enteric methane emissions while enhancing host energy utilization. This work provides a foundation for future mechanistic studies on the function and interactions of acetogens within the rumen microbiome, informing the development of strategies involved in redirecting hydrogen metabolism to improve ruminant production efficiency and reduce greenhouse gas emissions, thereby contributing to global efforts toward sustainable livestock systems.
Read the full journal article titled Metabolic versatility enables acetogens to colonize ruminants with diet-driven niche partitioning‘ in The ISME Journal. This article has been selected as Editor’s Choice for the month of August 2025
- Qiushuang Li, Institute of Subtropical Agriculture, Chinese Academy of Sciences, China
- Rong Wang, Institute of Subtropical Agriculture, Chinese Academy of Sciences, China
- Xiang Zhou, Institute of Subtropical Agriculture, Chinese Academy of Sciences, China
- Shuya Li, Wuxi University, China
- Shizhe Zhang, Institute of Subtropical Agriculture, Chinese Academy of Sciences, China
- Xiumin Zhang, Institute of Subtropical Agriculture, Chinese Academy of Sciences, China
- Wenxing Wang, Institute of Subtropical Agriculture, Chinese Academy of Sciences, China
- Jinzhen Jiao, Institute of Subtropical Agriculture, Chinese Academy of Sciences, China
- Peter H. Janssen, AgResearch Limited, New Zealand
- Emilio M. Ungerfeld, Instituto de Investigaciones Agropecuarias, Chile
- Volker Müller, Johann Wolfgang Goethe University, Germany
- Ralf Conrad, Max Planck Institute for Terrestrial Microbiology, Germany
- Chris Greening, Monash University, Australia
- Zhiliang Tan, Institute of Subtropical Agriculture, Chinese Academy of Sciences, China
- Bo Fu, Wuxi University, China
- Min Wang, Institute of Subtropical Agriculture, Chinese Academy of Sciences, China