Project description:Gut microbiome research is rapidly moving towards the functional characterization of the microbiota by means of shotgun meta-omics. Here, we selected a cohort of healthy subjects from an indigenous and monitored Sardinian population to analyze their gut microbiota using both shotgun metagenomics and shotgun metaproteomics. We found a considerable divergence between genetic potential and functional activity of the human healthy gut microbiota, in spite of a quite comparable taxonomic structure revealed by the two approaches. Investigation of inter-individual variability of taxonomic features revealed Bacteroides and Akkermansia as remarkably conserved and variable in abundance within the population, respectively. Firmicutes-driven butyrogenesis (mainly due to Faecalibacterium spp.) was shown to be the functional activity with the higher expression rate and the lower inter-individual variability in the study cohort, highlighting the key importance of the biosynthesis of this microbial by-product for the gut homeostasis. The taxon-specific contribution to functional activities and metabolic tasks was also examined, giving insights into the peculiar role of several gut microbiota members in carbohydrate metabolism (including polysaccharide degradation, glycan transport, glycolysis and short-chain fatty acid production). In conclusion, our results provide useful indications regarding the main functions actively exerted by the gut microbiota members of a healthy human cohort, and support metaproteomics as a valuable approach to investigate the functional role of the gut microbiota in health and disease.
Project description:The intestinal microbiota modulates host physiology and gene expression via mechanisms that are not fully understood. A recently discovered layer of gene expression regulation is N6-methyladenosine (m6A) and N6,2′ -O-dimethyladenosine (m6Am) modifications of mRNA. To unveil if these epitranscriptomic marks are affected by the gut microbiota, we performed methylated RNA-immunoprecipitation and sequencing (MeRIP-seq) to examine m6A-modifications in transcripts of mice displaying either a conventional, or a modified, or no gut microbiota and discovered that the microbiota has a strong influence on m6A- modifications in the cecum, and also, albeit to a lesser extent, in the liver, affecting pathways related to metabolism, inflammatory and antimicrobial responses . We furthermore analysed expression levels of several known writer and eraser enzymes and found the methyltransferase Mettl16 to be downregulated in absence of a microbiota. As a consequence, one of its targets, the S-adenosyl methionine synthase Mat2a was less expressed in mice without gut flora. We furthermore show that distinct commensal bacteria, Akkermansia muciniphila, Lactobacillus plantarum can affect specific m6A modifications. Together, we report here epitranscriptomic modifications as an additional level of interaction in the complex interplay between commensal bacteria and their host.
Project description:Opioids such as morphine have many beneficial properties as analgesics, however, opioids may induce multiple adverse gastrointestinal symptoms. We have recently demonstrated that morphine treatment results in significant disruption in gut barrier function leading to increased translocation of gut commensal bacteria. However, it is unclear how opioids modulate the gut homeostasis. By using a mouse model of morphine treatment, we studied effects of morphine treatment on gut microbiome. We characterized phylogenetic profiles of gut microbes, and found a significant shift in the gut microbiome and increase of pathogenic bacteria following morphine treatment when compared to placebo. In the present study, wild type mice (C57BL/6J) were implanted with placebo, morphine pellets subcutaneously. Fecal matter were taken for bacterial 16s rDNA sequencing analysis at day 3 post treatment. A scatter plot based on an unweighted UniFrac distance matrics obtained from the sequences at OTU level with 97% similarity showed a distinct clustering of the community composition between the morphine and placebo treated groups. By using the chao1 index to evaluate alpha diversity (that is diversity within a group) and using unweighted UniFrac distance to evaluate beta diversity (that is diversity between groups, comparing microbial community based on compositional structures), we found that morphine treatment results in a significant decrease in alpha diversity and shift in fecal microbiome at day 3 post treatment compared to placebo treatment. Taxonomical analysis showed that morphine treatment results in a significant increase of potential pathogenic bacteria. Our study shed light on effects of morphine on the gut microbiome, and its role in the gut homeostasis.
Project description:The gut microbiota promotes immune system development in early life, but the interactions between the gut metabolome and immune cells in the neonatal gut remains largely undefined. Here, we demonstrate that the neonatal gut is uniquely enriched with neurotransmitters, including serotonin; specific gut bacteria produce serotonin directly while downregulating monoamine oxidase A to limit serotonin breakdown. Serotonin directly signals to T cells to increase intracellular indole-3-acetaldehdye to inhibit mTOR activation and thereby promotes the differentiation of regulatory T cells, both ex vivo and in vivo in the neonatal intestine. Oral gavage of serotonin into neonatal mice leads to long-term T cell-mediated antigen-specific immune tolerance towards both dietary antigens and commensal bacteria. Together, our study has uncovered an important role for unique gut bacteria to increase serotonin availability in the neonatal gut and a novel function of gut serotonin to shape T cell response to dietary antigens and commensal bacteria to promote immune tolerance in early life.
Project description:The gut microbiota promotes immune system development in early life, but the interactions between the gut metabolome and immune cells in the neonatal gut remains largely undefined. Here, we demonstrate that the neonatal gut is uniquely enriched with neurotransmitters, including serotonin; specific gut bacteria produce serotonin directly while downregulating monoamine oxidase A to limit serotonin breakdown. Serotonin directly signals to T cells to increase intracellular indole-3-acetaldehdye to inhibit mTOR activation and thereby promotes the differentiation of regulatory T cells, both ex vivo and in vivo in the neonatal intestine. Oral gavage of serotonin into neonatal mice leads to long-term T cell-mediated antigen-specific immune tolerance towards both dietary antigens and commensal bacteria. Together, our study has uncovered an important role for unique gut bacteria to increase serotonin availability in the neonatal gut and a novel function of gut serotonin to shape T cell response to dietary antigens and commensal bacteria to promote immune tolerance in early life.
Project description:The gut microbiota promotes immune system development in early life, but the interactions between the gut metabolome and immune cells in the neonatal gut remains largely undefined. Here, we demonstrate that the neonatal gut is uniquely enriched with neurotransmitters, including serotonin; specific gut bacteria produce serotonin directly while downregulating monoamine oxidase A to limit serotonin breakdown. Serotonin directly signals to T cells to increase intracellular indole-3-acetaldehdye to inhibit mTOR activation and thereby promotes the differentiation of regulatory T cells, both ex vivo and in vivo in the neonatal intestine. Oral gavage of serotonin into neonatal mice leads to long-term T cell-mediated antigen-specific immune tolerance towards both dietary antigens and commensal bacteria. Together, our study has uncovered an important role for unique gut bacteria to increase serotonin availability in the neonatal gut and a novel function of gut serotonin to shape T cell response to dietary antigens and commensal bacteria to promote immune tolerance in early life.
Project description:To explore the bacterial community profile of the gut of the African palm weevil and to identify the abundance and diversity of lignin degradation-associated bacteria in each gut segment.