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Roux-en-Y gastric bypass (RYGB) rearranges the gastrointestinal tract and reduces gastric acid secretions. Therefore, pH could be one of the factors that change microbiome after RYGB. Using mixed-cultures and co-cultures of species enriched after RYGB, I showed that as small as 0.5 units higher gut pH can aid in the survival of acid-sensitive microorganisms after RYGB and alter gut microbiome function towards the production of weight loss-associated metabolites. By comparing microbiome after two different bariatric surgeries, RYGB and laparoscopic adjustable gastric banding (LAGB), I revealed that gut microbiome structure and metabolism after RYGB are remarkably different than LAGB, and LAGB change microbiome minimally. Given the distinct RYGB alterations to the microbiome, I examined the contribution of the microbiome to weight loss. Analyses revealed that Fusobacterium might lessen the success of RYGB by producing putrescine, which may enhance weight-gain and could serve as biomarker for unsuccessful RYGB.
Finally, I showed that RYGB alters the luminal and the mucosal microbiome. Changes in gut microbial metabolic products occur in the short-term and persist over the long-term. Overall, the work in this dissertation provides insight into how the gut microbiome structure and function is altered after bariatric surgery, and how these changes potentially affect the host metabolism. These findings will be helpful in subsequent development of microbiome-based therapeutics to treat obesity.
Locusts are generalist herbivores meaning that they are able to consume a variety of plants. Because of their broad diet, and ability to respond rapidly to a favorable environment with giant swarms of voracious insects, they are dangerous pests. Their potential impacts on humans increase dramatically when individuals switch from their solitarious phase to their gregarious phase where they congregate and begin marching and eventually swarming together. These swarms, often billions strong, can consume the vegetation of enormous swaths of land and can travel hundreds of kilometers in a single day producing a complex threat to food security. To better understand the biology of these important pests we explored the gut microbiome of the South American locust (Schistocerca cancellata). We hypothesized generally that the gut microbiome in this species would be critically important as has been shown in many other species. We extracted and homogenized entire guts from male S. cancellata, and then extracted gut microbiome genomic DNA. Genomic DNA was then confirmed on a gel. The initial extractions were of poor quality for sequencing, but subsequent extractions performed by collaborators during troubleshooting at Southern Illinois University Edwardsville proved more useful and were used for PCR. This resulted in the detections of the following bacterial genera in the gut of S. cancellata: Enterobacter, Enterococcus, Serratia, Pseudomonas, Actinobacter, and Weisella. With this data, we are able to speculate about the physiological roles that they hold within the locust gut generating hypotheses for further testing. Understanding the microbial composition of this species’ gut may help us better understand the locust in general in an effort to more sustainably manage them.
The incidence of childhood obesity has become increasingly prevalent in the United States in recent years. The development of obesity at any age, but especially in adolescence, can have lasting negative effects in the form of cardiometabolic disease, increased incurred healthcare costs, and potential negative effects on quality of life. In recent years, a rising trend of obesity, in both adults and adolescents, has been observed in lower income and ethnic groups. Increased adiposity can be influenced by modifiable factors -(physical activity, caloric intake, or sleep) or by non-modifiable factors (ethnicity, genetic predispositions, and socioeconomic status). The influence of these factors can be observed in individuals of all ages, including infants. A common indicator of the development of childhood obesity is rapid weight gain (RWG) within an infant’s first year of life. The composition of the gut microbiome can act as a predictor for RWG and the development of childhood obesity. Infants are exposed to an immense microbial load when they are born and their gut microbiome is continually diversified through their method of feeding and the subsequent introduction to solid foods. While currently understudied, it is understood that cultural and socioeconomic factors influence the development of the gut microbiome, which is further explored in this analysis. The DNA from 51 fecal samples from infants ranging from 3 weeks to 12 months in age was extracted and sequenced using next-generation sequencing, and the resulting sequences were analyzed using QIIME 2. Results from alpha-diversity and beta-diversity metrics showed significant differences in the gut microbiome of infants when comparing groups based on baby race/ethnicity, household income, and mom’s education. These findings suggest the importance of sociodemographic characteristics in shaping the gut microbiome and suggest the importance of future studies including diverse populations in gut microbiome work.