Investigating the respiratory chain of a human gut symbiont

Abstract

The gut microbiota is essential for human health, helping humans break down nutrients that would be indigestible without the bacterial population. An important member of this group is Bacteroides. These bacteria are polysaccharide utilizers that were previously considered strict anaerobes (cannot grow in the presence of oxygen). However, Bacteroides live at the oxic/anoxic interface of the colon, near the epithelial cells, where oxygen levels are around 1,000 ppm (nanaerobic). Bacteroides’ survival in this environment is thus dependent on their ability to efficiently conserve energy. Previous work has shown that Bacteroides use a cytochrome bd-type oxygen reductase, which reduces oxygen to water. Here, I will show the following properties of the Bacteroides respiratory chain: 1) Bacteroides can simultaneously respire in both anaerobic and nanaerobic conditions, a unique ability that seems to fit the demands of the environment in the mammalian colon and 2) Bacteroides species are able to remodel exogenous quinone derivatives through a similar pathway to humans. The results of these investigations clearly show the importance of Bacteroides energy metabolism in their ability to adapt to their host environment.