Figure 1: Dynamics of hydrogen generated by Bacteroides settled in the intestinal wall. Note: (1) Bacteroides bound to dimeric IgA antibody form colonies in intestinal epithelial cells. (2) Bacteroides produce hydrogen. (3) The produced hydrogen eliminates hydroxyl radicals generated inside the intestinal epithelial cells and protects the intestinal wall from oxidative stress. (4) Hydrogen may also be involved in activating the metabolism of Firmicutes by colonies of Bacteroides. (5) Excess hydrogen diffuses across the membrane and surplus hydrogen enters the bloodstream to travel throughout the body.