Generate Electricity through Flavin Mononucleotide-Mediated Extracellular Electron Transfer to Upregulate Epithelial Type I Collagen Expression and Thereby Promote Microbial Adhesion to Intestine.

The mechanism behind how flavin mononucleotide (FMN)-producing bacteria attach to a host intestine remains unclear. In order to address this issue, this study isolated the Gram-positive bacteria from Mongolian fermented Airag, named . MA. These bacteria were further employed as the model microbes, and their electrogenic properties were first identified by their significant expression of type II NADH-quinone oxidoreductase. This study also demonstrated that the electrical activity of MA can be conducted through flavin mononucleotide (FMN)-based extracellular electron transfer, which is highly dependent on the presence of a carbon source in the medium. Our data show that approximately 15 µM of FMN, one of the key electron donors for the generation of electricity, can be produced from MA, as they were cultured in the presence of lactulose for 24 h. We further demonstrated that the electrical activity of MA can promote microbial adhesion and can thus enhance the colonization effectiveness of Caco-2 cells and mouse cecum. Such enhanced adhesiveness was attributed to the increased expression of type I collagens in the intestinal epithelium after treatment with MA. This study reveals the mechanism behind the electrogenic activity of MA and shows how the bacteria utilize electricity to modulate the protein expression of gut tissue for an enhanced adhesion process.