Hydrogen Availability Is Dependent on the Actions of Both Hydrogen-Producing and Hydrogen-Consuming Microbes.

Hydrogen gas (H2) is produced by H2-producing microbes in the gut during polysaccharide fermentation. Gut microbiome also includes H2-consuming microbes utilizing H2 for metabolism: methanogens producing methane, CH4, and sulfate-reducing bacteria producing hydrogen sulfide, H2S. H2S is not measured in the evaluation of gaseous byproducts of microbial fermentation. We hypothesize that the availability of measured H2 depends on both hydrogen producers and hydrogen consumers by measuring H2 in vitro and in vivo. In the in vitro study, groups were Bacteroides thetaiotaomicron (B. theta, H2 producers), Desulfovibrio vulgaris (D. vulgaris, H2 consumers), and D. vulgaris + B. theta combined. Gas samples were collected at 2 h and 24 h after incubation and assayed for H2, CH4, and H2S. In the in vivo study Sprague-Dawley rats were gavaged with suspended bacteria in four groups: B. theta, D. vulgaris, combined, and control. Gas was analyzed for H2 at 60 min. In the in vitro experiment, H2 concentration was higher in the combined group (188 ± 93.3 ppm) compared with D. vulgaris (27.17 ± 9.6 ppm) and B. theta groups (34.2 ± 29.8 ppm; P < 0.05); H2S concentration was statistically higher in the combined group (10.32 ± 1.5 ppm) compared with B. theta (0.19 ± 0.03 ppm) and D. vulgaris group (3.46 ± 0.28 ppm; P < 0.05). In the in vivo study, H2 concentrations were significantly higher in the B. theta group (44.3 ± 6.0 ppm) compared with control (31.8 ± 4.3) and the combined group (34.2 ± 8.7, P < 0.05). This study shows that sulfate-reducing bacteria could convert available H2 to H2S, leading to measured hydrogen levels that are dependent on the actions of both H2 producers and H2 consumers.