Project description:Chronic diseases arise when pathophysiological processes achieve a steady state by self-reinforcing. Here, we explored the possibility of a self-reinforcement state in a common condition, chronic constipation, where alterations of the gut microbiota have been reported. The functional impact of the microbiota shifts on host physiology remains unclear, however we hypothesized that microbial communities adapted to slow gastrointestinal transit affect host functions in a way that reinforces altered transit, thereby maintaining the advantage for microbial self-selection. To test this, we examined the impact of pharmacologically (loperamide)-induced constipation (PIC) on the structural and functional profile of altered gut microbiota. PIC promoted changes in the gut microbiome, characterized by decreased representation of butyrate-producing Clostridiales, decreased cecal butyrate concentration and altered metabolic profiles of gut microbiota. PIC-associated gut microbiota also impacted colonic gene expression, suggesting this might be a basis for decreased gastrointestinal (GI) motor function. Introduction of PIC-associated cecal microbiota into germ-free (GF) mice significantly decreased GI transit time. Our findings therefore support the concept that chronic diseases like constipation are caused by disease-associated steady states, in this case, caused by reciprocating reinforcement of pathophysiological factors in host-microbe interactions. We used microarrays to detail the global gene expression profile in the proximal colon smooth muscle tissues of germ-free, conventionalized, or specific pathogen free mouse C57Bl/6 female and male specific pathogen free (SPF) mice were bred and housed in the animal care facility at the University of Chicago. Mice of 8–10 weeks of age were treated with 0.1% loperamide in the drinking water for 7 days. Age matched, germ-free (GF) C57Bl/6 mice were gavaged orally with cecal luminal contents harvested from control or loperamide-treated C57Bl/6 donor mice. Recipient mice were sacrificed 4 weeks post-colonization.

Project description:Genome scale metabolic model of Drosophila gut microbe Acetobacter fabarum Abstract - An important goal for many nutrition-based microbiome studies is to identify the metabolic function of microbes in complex microbial communities and their impact on host physiology. This research can be confounded by poorly understood effects of community composition and host diet on the metabolic traits of individual taxa. Here, we investigated these multiway interactions by constructing and analyzing metabolic models comprising every combination of five bacterial members of the Drosophila gut microbiome (from single taxa to the five-member community of Acetobacter and Lactobacillus species) under three nutrient regimes. We show that the metabolic function of Drosophila gut bacteria is dynamic, influenced by community composition, and responsive to dietary modulation. Furthermore, we show that ecological interactions such as competition and mutualism identified from the growth patterns of gut bacteria are underlain by a diversity of metabolic interactions, and show that the bacteria tend to compete for amino acids and B vitamins more frequently than for carbon sources. Our results reveal that, in addition to fermentation products such as acetate, intermediates of the tricarboxylic acid (TCA) cycle, including 2-oxoglutarate and succinate, are produced at high flux and cross-fed between bacterial taxa, suggesting important roles for TCA cycle intermediates in modulating Drosophila gut microbe interactions and the potential to influence host traits. These metabolic models provide specific predictions of the patterns of ecological and metabolic interactions among gut bacteria under different nutrient regimes, with potentially important consequences for overall community metabolic function and nutritional interactions with the host.IMPORTANCE Drosophila is an important model for microbiome research partly because of the low complexity of its mostly culturable gut microbiota. Our current understanding of how Drosophila interacts with its gut microbes and how these interactions influence host traits derives almost entirely from empirical studies that focus on individual microbial taxa or classes of metabolites. These studies have failed to capture fully the complexity of metabolic interactions that occur between host and microbe. To overcome this limitation, we reconstructed and analyzed 31 metabolic models for every combination of the five principal bacterial taxa in the gut microbiome of Drosophila This revealed that metabolic interactions between Drosophila gut bacterial taxa are highly dynamic and influenced by cooccurring bacteria and nutrient availability. Our results generate testable hypotheses about among-microbe ecological interactions in the Drosophila gut and the diversity of metabolites available to influence host traits.

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