Sharpea and Kandleria are lactic acid producing rumen bacteria that do not change their fermentation products when co-cultured with a methanogen

Sharpea and Kandleria are associated with low CH4 emitting sheep rumen samples. Pure cultures of four strains of each genus were studied in culture, and the genomes of nine strains were analysed, to understand the physiology of these bacteria. All eight cultures grew equally well with D glucose, D fructose, D galactose, cellobiose, and sucrose. D-Lactate was the major end product, with small amounts of the mixed acid fermentation products formate, acetate and ethanol. Genes encoding the enzymes necessary for this fermentation pattern were found in the genomes of five strains of Sharpea and four of Kandleria. Strains of Sharpea produced traces of hydrogen gas in pure culture, but strains of Kandleria did not. In agreement with this, the genomes of Sharpea contained genes coding for hydrogenases while those of Kandleria did not. It was speculated that, in co-culture with a methanogen, Sharpea and Kandleria might change their fermentation pattern from a predominately homolactic to a predominately mixed acid fermentation, which would result in a decrease in lactate production and an increase in formation of acetate and perhaps ethanol, but this did not happened. Sharpea and Kandleria did not change their fermentation products when they grew with M. olleyae, a methanogen that can use both H2 and formate, and lactate remained the major end product. The results of this study therefore support a hypothesis that explains the link between lower methane yields and larger populations of Sharpea and Kandleria in the rumens of sheep. The proposed mechanism predicted that, in the complex rumen environment, Sharpea and Kandleria produce lactate as their major end product.