( roides thetaiotaomicron begin a fermen...)Gut microbes' partnership helps body extract energy from food, store it as fat

But B. thetaiotaomicron doesn't just work in a simple partnership with its host. The human gut contains hundreds, and perhaps thousands, of different microbial species, and the functions they perform affect each other and their hosts.

Gordon's lab models the interactions between friendly gut microbes and their hosts using gnotobiotic mice. These mice are raised in a manner that keeps them germ-free. They are then colonized with one or more human gut-derived microbes to study how microbial-microbial and microbial-host interactions affect digestive health.

Buck Samuel, a doctoral student in Gordon's lab, began to probe the influence of Methanobrevibacter smithii, an archaeon. Originally identified in the 1970s and mistaken for a primitive form of bacteria, archaea initially became famous because of their ability to live in extreme environments where nothing else could survive, such as hot springs. Scientists first isolated archaea from the human intestine in 1982, and have recently recognized M. smithii as the most common archaeon in human intestines.

In addition to its prevalence, M. smithii was an intriguing target for study because of its ability to consume hydrogen and other byproducts of bacterial digestion of polysaccharides. Accumulation of such byproducts slows polysaccharide digestion. Samuel and Gordon speculated that M. smithii could improve the overall efficiency of digestion of dietary polysaccharides, and wondered whether it also affected which types of polysaccharides are most coveted by intestinal bacteria.

Samuel colonized one group of gnotobiotic mice with the polysaccharide-digesting bacterium B. thetaiotaomicron. Another group was colonized with M. smithii, while a third group received both B. thetaiotaomicron and M. smithii.

The archaeon's presence
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Source:Washington University School of Medicine