Fig. 3
Influence of methanogenesis on butyrate production products in a synthetic gut community and the human gut microbiota. Methane (A), H2 (B), and butyrate (C) production by a 9-species synthetic human gut community grown with (shaded bars) and without (open bars) the addition of M. smithii. Butyrate was measured in three successive subcultures, with a new inoculum of M. smithii added at each passage. In a human cohort consuming a resistant potato starch supplement, breath and fecal samples were used to determine weekly average breath CH4 (D), breath H2 (E), and fecal butyrate (F) in individuals with and without active gut methanogenesis, defined as at least one breath methane measurement greater than 4 ppm CH4 in the measurement period (MG) or no breath measurements over 4 ppm in the same period (non-MG). Error bars indicate SEM. Statistical significance calculated using two-sided Student’s two-sample t-tests (*p < 0.05; **p < 0.01; ***p < 0.001). One breath H2 measurement shown in the methanogenic group with a value over 60 ppm (data point shown in red) was excluded from statistical analysis