Use of genomics and transcriptomics to identify strategies to lower ruminal methanogenesis

Abstract Text: Globally, methane emissions account for 40-45% of greenhouse gas emissions (GHG) from ruminant livestock with over 90% of these emissions arising from enteric fermentation.   Reduction of carbon dioxide to methane is critical for efficient ruminal fermentation as it prevents the accumulation of reducing equivalents in the rumen.   Methanogens exist in a symbiotic relationship with rumen protozoa, fungi and within biofilms associated with feed and the rumen wall.   Genomics and transcriptomics are playing an increasingly important role in defining the ecology of ruminal methanogenesis and identifying avenues for its mitigation.   Genomic approaches have provided information on changes in abundances as well as the species composition of the methanogen community among ruminants that vary naturally in their methane emissions, their feed efficiency and response to methane mitigators.   Sequencing the genomes of rumen methanogens has provided insight into surface proteins that may prove useful in the development of vaccines and allowed assembly of biochemical pathways for use in chemogenomic approaches to lowering ruminal methane emissions.   Metagenomics and metatranscriptomic analysis of entire rumen microbial communities are providing new perspectives on how methanogens interact with other members of this ecosystem and how these relationships may be altered to reduce methanogenesis.   Identification of community members that produce anti-methanogen agents that either inhibit or kill methanogens could lead to the identification of new mitigation approaches.   Discovey of lytic archaeophage that specifically lyse methanogens is one such example.   Efforts in using genomic data to alter methanogenesis have been hampered by a lack of sequence information that is specific to the microbial community of the rumen.  Programs such as the “Hungate 1000” and the “Global Rumen Census” are increasing the breadth and depth of our understanding of global ruminal microbial communities, steps that are key to using these tools to further define the science of ruminal methanogenesis.

Keywords: ruminal methanogenesis, genomics, transcriptomics