Genetic and Biochemical Analysis of Anaerobic Respiration in Bacteroides fragilis and Its Importance <i>In Vivo</i>
Takeshi Ito, Rene Gallegos, Leigh M. Matano, Nicole Butler, Noam Hantman, Matthew Kaili, Michael J. Coyne, Laurie E. Comstock, Michael H. Malamy, Blanca Barquera
Abstract
Bacteroides species are abundant in the human intestine and provide numerous beneficial properties to their hosts. The ability of Bacteroides species to convert host and dietary glycans and polysaccharides to energy is paramount to their success in the human gut. We know a great deal about the molecules that these bacteria extract from the human gut but much less about how they convert those molecules into energy. Here, we show that B. fragilis has a complex respiratory pathway with two different enzymes that transfer electrons from NADH to quinone and a third enzyme complex that may use an electron donor other than NADH. Although fermentation has generally been believed to be the main mechanism of energy generation in Bacteroides , we found that a mutant lacking one of the NADH:quinone oxidoreductases was unable to compete with the wild type in the mammalian gut, revealing the importance of respiration to these abundant gut symbionts.