[Abstract] Quinella is a genus of iconic rumen bacteria first reported in 1913. There are no cultures of these bacteria, and information on its physiology is scarce and contradictory. Increased abundance of Quinella was found in the rumens of some sheep that emit low amounts of methane (CH4) relative to their feed intake, but how Quinella contributes to low CH4 emissions is not known. We concentrated Quinella cells from rumen contents, extracted and sequenced DNA, and reconstructed Quinella genomes that were >90% complete with as little as 0.20% contamination. Bioinformatic analyses of the encoded proteins showed that lactate and propionate formation are major fermentation pathways, while a potential uptake hydrogenase suggests that Quinella might use free hydrogen (H2). In all these pathways, there is no production of H2, a major precursor of CH4, which is consistent with the lower CH4 emissions from those sheep with high abundances of this bacterium.