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Dissecting the in Vivo Metabolic Potential of Two Human Gut Acetogens

Center for Genome Sciences, Washington University School of Medicine, St. Louis, Missouri 63108, USA.
Journal of Biological Chemistry (Impact Factor: 4.57). 05/2010; 285(29):22082-90. DOI: 10.1074/jbc.M110.117713
Source: PubMed

ABSTRACT Fermenting microbial communities generate hydrogen; its removal through the production of acetate, methane, or hydrogen sulfide modulates the efficiency of energy extraction from available nutrients in many ecosystems. We noted that pathway components for acetogenesis are more abundantly and consistently represented in the gut microbiomes of monozygotic twins and their mothers than components for methanogenesis or sulfate reduction and subsequently analyzed the metabolic potential of two sequenced human gut acetogens, Blautia hydrogenotrophica and Marvinbryantia formatexigens in vitro and in the intestines of gnotobiotic mice harboring a prominent saccharolytic bacterium. To do so, we developed a generally applicable method for multiplex sequencing of expressed microbial mRNAs (microbial RNA-Seq) and, together with mass spectrometry of metabolites, showed that these organisms have distinct patterns of substrate utilization. B. hydrogenotrophica targets aliphatic and aromatic amino acids. It increases the efficiency of fermentation by consuming reducing equivalents, thereby maintaining a high NAD(+)/NADH ratio and boosting acetate production. In contrast, M. formatexigens consumes oligosaccharides, does not impact the redox state of the gut, and boosts the yield of succinate. These findings have strategic implications for those who wish to manipulate the hydrogen economy of gut microbial communities in ways that modulate energy harvest.

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    • "Members of this phylum generally act as mutualists by aiding in the digestion of complex carbohydrates, promoting gut development , modulating the immune system, and protecting against colonization by pathogens (Round and Mazmanian, 2009; Smith et al., 2006; Thomas et al., 2011). As metabolically pliable organisms, Bacteroidetes also help to support a diverse gut community through syntrophic interactions with other microbes (Fischbach and Sonnenburg, 2011; Rey et al., 2010). Evidence suggests that the capacity of a bacterium to survive in a polymicrobial environment is related to the elaboration of interbacterial antagonistic factors. "
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    • "sibility of evaluating more simplified , defined communities on the host metabolomic profile is a promising avenue to gain mechanistic insights . Simplified and defined model systems have been used extensively to study functional properties of common gut residents in vivo ( Sonnenburg et al . , 2006 ; Samuel et al . , 2007 ; Marco et al . , 2010 ; Rey et al . , 2010 ; Faith et al . , 2011 ) . Our use of one - and two - member model communities indicates that there are aspects of the host metabolome that are conserved between these simplified ecosystems and an entire human micro - biota , specifically the common depletion of meta - bolites that are present in GF mice . An important remaining questio"
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    The ISME Journal 06/2013; 7(10). DOI:10.1038/ismej.2013.89 · 9.27 Impact Factor
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    • "Additionally, the augmented B. thetaiotaomicron levels lead to increased production of short-chain fatty acids, which can be used as source of nutrition by the human host. Alternatively, gut communities that lack methanogens can instead process excess H 2 through acetogenesis (Rey et al. 2010). In this case the acetogen Bacteroides hydrogenotrophica fills the role of H 2 consumer, with similar benefits to both the microbes involved in the syntrophic interaction and the host. "
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