1. Vitamin B12 as a Modulator of Gut Microbial Ecology
Patrick H. Degnan, Michiko E. Taga, Andrew L. Goodman 
Cell Metabolism 
Volume 20, Issue 5, Pages (November 2014)
DOI: /j.cmet
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2. Cell Metabolism 2014 20, 769-778DOI: (10.1016/j.cmet.2014.10.002)
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3. Figure 1 Representative Examples of Corrinoid Structural Diversity
See Allen and Stabler, 2008 and Renz, 1999.
Cell Metabolism  , DOI: ( /j.cmet )
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4. Figure 2 Microbial Corrinoid Metabolism in the Gut
In coprophagic and ruminant animals, gut microbes provide a direct source of cobalamin (direct effect) (Girard et al., 2009). In some insects, corrinoids are essential cofactors for obligate symbionts that provide key nutrients to the host (indirect effect) (McCutcheon et al., 2009). Competition and exchange of corrinoids likely shape gut microbial community composition and expressed functions in humans and other animals (microbiome remodeling) (Allen and Stabler, 2008; Goodman et al., 2011; Seth and Taga, 2014).
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5. Figure 3
Corrinoid Composition of Microbial Communities Measured by LCMS
(A) The average corrinoid composition of fecal samples from 18 humans in the absence of cobalamin supplementation (Human); a groundwater enrichment community amended with trichloroethene (GW); and bovine rumen (Rumen) is shown (adapted with permission from Allen and Stabler, 2008; Girard et al., 2009; Men et al., 2014b).
(B) Corrinoid composition of fecal samples from 20 individuals (adapted with permission from Allen and Stabler, 2008). Asterisks indicate individuals supplemented daily with ≤25 μg cobalamin. Double asterisks indicate individuals supplemented daily with ≤1,000 μg cobalamin. Corrinoid abbreviations are defined in Box 1.
Cell Metabolism  , DOI: ( /j.cmet )
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