Project description:EMG produced TPA metagenomics assembly of the Regulators of Gut Motility Revealed by a Gnotobiotic Model of Diet-Microbiome Interactions Related to Travel (Gut microbiota and motility) data set.
Project description:We illustrate an approach for integrating preclinical gnotobiotic animal models with human studies to understand the contributions of perturbed gut microbiota development to childhood undernutrition, and to identify new microbiota-directed therapeutic concepts/leads. Combining metabolomic and proteomic analyses of serially collected plasma samples with metagenomic analyses of serially collected fecal samples, we characterized the biological state of Bangladeshi children with severe acute malnutrition (SAM) as they transitioned to moderate acute malnutrition (MAM) after standard treatment. Gnotobiotic mice were subsequently colonized with a defined consortium of bacterial strains representing different stages of microbiota development in healthy children from Bangladesh. Administering different combinations of Bangladeshi complementary food ingredients to colonized mice and germ-free controls revealed diet-dependent changes in representation and metabolism of targeted weaning-phase strains, including accompanying increases in branched-chain amino acids, plus diet- and colonization-dependent augmentation of IGF-1/mTOR signaling. Host and microbial effects of microbiota-directed complementary food (MDCF) prototypes were subsequently examined in gnotobiotic mice colonized with post-SAM MAM microbiota and in gnotobiotic piglets colonized with a defined consortium of targeted age- and growth-discriminatory bacteria. Finally, ar andomized, double-blind study revealed a lead MDCF that affected the representation of targeted bacterial taxa and increased levels of biomarkers and mediators of growth, bone formation, neurodevelopment, and immune function.
Project description:Gastrointestinal microbes modulate peristalsis and stimulate the enteric nervous system (ENS), whose development, as in the central nervous system (CNS), continues into the murine postweaning period. Given that adult CNS function depends on stimuli received during critical periods of postnatal development, we hypothesized that adult ENS function, namely motility, depends on microbial stimuli during similar critical periods. We gave fecal microbiota transplantation (FMT) to germ-free mice at weaning or as adults and found that only the mice given FMT at weaning recovered normal transit, while those given FMT as adults showed limited improvements. RNAseq of colonic muscularis propria revealed enrichments in neuron developmental pathways in mice exposed to gut microbes earlier in life, while mice exposed later – or not at all – showed exaggerated expression of inflammatory pathways. These findings highlight a microbiota-dependent sensitive period in ENS development, pointing to potential roles of the early life microbiome in later life dysmotility.
Project description:The gut microbiota, immune system, and enteric nervous system interact to regulate adult gut physiology. Yet the mechanisms establishing gut physiology during development remain unknown. We report that in developing zebrafish, enteroendocrine cells produced IL-22 in response to microbial signals before lymphocytes populate the gut. In larvae, IL-22 shaped the gut microbiota, increased Lactobacillaceae abundance and ghrelin expression to promote gut motility. Impaired motility and ghrelin expression were restored in il22-/- zebrafish by transfer of microbiota from wild-type zebrafish or by monoassociation with Lactobacillus plantarum. IL-22-deficient mice had impaired gut motility and reduced ghrelin expression in early life too, indicating a conserved function. Thus, before immune system maturation, enteroendocrine cells regulate early-life gut function by controlling the microbiota via IL-22.
Project description:Organ development relies on interactions among different cell types that form three-dimensional structures to carry out specific tasks. This process often involves active migration of progenitor cells toward specific positions within the embryo, where the cells then become immotile and form stable connections among each other and with neighboring cell types. Yet, surprisingly little is known about processes of motility loss and the emerging organization of the cells at the site where the organ forms. In this work, we study these the process of motility loss processes using zebrafish primordial germ cells as an in vivo model. We show that changes in embryonic tissues as well as cell-autonomous events regulate germ cells’ behavior as they arrive at their target region. Importantly, we find that reduction in germ cell motility is correlated with the decay of RNA encoding for Dead end 1 (Dnd1), a conserved vertebrate RNA-binding protein that is essential for PGC migration. Indeed, decreasing or increasing the level of Dnd1 results in a premature or delayed stop to motility, respectively. These findings represent a novel RNA decay-based mechanism for timing the duration of cell migration in vivo.
Project description:Motility in Listeria monocytogenes is negatively regulated within the mammalian host in response to temperature through a complex interplay between positively acting and negatively acting regulators. Motility genes are expressed under saprophytic conditions where the temperature is 30ºC or less. Motility is costly on cellular resources due to the large molecular structures that need to be synthesized, and the proton motive force required to produce flagellar rotation. Under stressful environmental conditions there is a trade off between motility and energy conservation and bacteria typically repress motility when adverse conditions are encountered. Here we investigated the impact of the SigB-mediated general stress response on the regulation of motility in L. monocytogenes and sought to elucidate the regulatory steps involved. We show that an rsbX mutation that compromises the ability to inactivate the stressosome, the sensory hub at the top of the SigB activation pathway, results in motility repression. Escaping from this repressed state occurred through the acquisition of mutations that decreased SigB activity. Flagellar expression was abolished in these mutants and a transcriptomic analysis revealed that the entire flagellar operon is strongly repressed. The motility anti-repressor gene gmaR was also downregulated in an ΔrsbX background. These effects can be reversed by providing functional copies of rsbX or gmaR in trans. Deletion of an internal SigB dependent promoter that produces an antisense RNA for the large motility operon (including gmaR) restores the ability to produce flagellin in the ΔrsbX background. A similar phenotype is observed by deleting MogR, which acts as a negative regulator of flagella motility. Stressosome mutations that negatively affect SigB activity result in derepressed motility whereas those that increase SigB activity result in a decreased motility phenotype similar to the ΔrsbX strain. Overall, the data indicate that stress sensing via the stressosome negatively impacts motility in L. monocytogenes and shows that the general stress response can take priority over motility when L. monocytogenes encounters harsh environmental conditions.
Project description:The human gut microbiota is an important metabolic organ, yet little is known about how its individual species interact, establish dominant positions, and respond to changes in environmental factors such as diet. In this study, gnotobiotic mice were colonized with an artificial microbiota comprising 12 sequenced human gut bacterial species and fed oscillating diets of disparate composition. Rapid, reproducible, and reversible changes in the structure of this assemblage were observed. Time-series microbial RNA-Seq analyses revealed staggered functional responses to diet shifts throughout the assemblage that were heavily focused on carbohydrate and amino acid metabolism. High-resolution shotgun metaproteomics confirmed many of these responses at a protein level. One member, Bacteroides cellulosilyticus WH2, proved exceptionally fit regardless of diet. Its genome encoded more carbohydrate active enzymes than any previously sequenced member of the Bacteroidetes. Transcriptional profiling indicated that B. cellulosilyticus WH2 is an adaptive forager that tailors its versatile carbohydrate utilization strategy to available dietary polysaccharides, with a strong emphasis on plant-derived xylans abundant in dietary staples like cereal grains. Two highly expressed, diet-specific polysaccharide utilization loci (PULs) in B. cellulosilyticus WH2 were identified, one with characteristics of xylan utilization systems. Introduction of a B. cellulosilyticus WH2 library comprising >90,000 isogenic transposon mutants into gnotobiotic mice, along with the other artificial community members, confirmed that these loci represent critical diet-specific fitness determinants. Carbohydrates that trigger dramatic increases in expression of these two loci and many of the organism’s 111 other predicted PULs were identified by RNA-Seq during in vitro growth on 31 distinct carbohydrate substrates, allowing us to better interpret in vivo RNA-Seq and proteomics data. These results offer insight into how gut microbes adapt to dietary perturbations at both a community level and from the perspective of a well-adapted symbiont with exceptional saccharolytic capabilities, and illustrate the value of artificial communities. 611 samples total (221 from experiment 1, 390 from experiment 2). Evaluation of changes in an artificial gut community's structure over time as a result of dietary oscillation.
Project description:The human gut microbiota is an important metabolic organ, yet little is known about how its individual species interact, establish dominant positions, and respond to changes in environmental factors such as diet. In this study, gnotobiotic mice were colonized with an artificial microbiota comprising 12 sequenced human gut bacterial species and fed oscillating diets of disparate composition. Rapid, reproducible, and reversible changes in the structure of this assemblage were observed. Time-series microbial RNA-Seq analyses revealed staggered functional responses to diet shifts throughout the assemblage that were heavily focused on carbohydrate and amino acid metabolism. High-resolution shotgun metaproteomics confirmed many of these responses at a protein level. One member, Bacteroides cellulosilyticus WH2, proved exceptionally fit regardless of diet. Its genome encoded more carbohydrate active enzymes than any previously sequenced member of the Bacteroidetes. Transcriptional profiling indicated that B. cellulosilyticus WH2 is an adaptive forager that tailors its versatile carbohydrate utilization strategy to available dietary polysaccharides, with a strong emphasis on plant-derived xylans abundant in dietary staples like cereal grains. Two highly expressed, diet-specific polysaccharide utilization loci (PULs) in B. cellulosilyticus WH2 were identified, one with characteristics of xylan utilization systems. Introduction of a B. cellulosilyticus WH2 library comprising >90,000 isogenic transposon mutants into gnotobiotic mice, along with the other artificial community members, confirmed that these loci represent critical diet-specific fitness determinants. Carbohydrates that trigger dramatic increases in expression of these two loci and many of the organism’s 111 other predicted PULs were identified by RNA-Seq during in vitro growth on 31 distinct carbohydrate substrates, allowing us to better interpret in vivo RNA-Seq and proteomics data. These results offer insight into how gut microbes adapt to dietary perturbations at both a community level and from the perspective of a well-adapted symbiont with exceptional saccharolytic capabilities, and illustrate the value of artificial communities. 116 samples total. In 26 of these samples, we evaluated community-wide gene expression using RNA isolated from the feces of a gnotobiotic mouse harboring an artificial community comprised of 12 human gut microbes. For these samples, we sought to determine the extent to which community gene expression is altered as a result of dietary oscillation. In the other 90 samples, we evaluated gene expression in a single species (B. cellulosilyticus WH2) grown in a defined medium supplemented with a single mono-, oligo-, or polysaccharide. For these samples, we sought to identify genes (particularly polysaccharide utilization loci) whose expression was significantly increased as a result of exposure to particular carbohydrates.