Variations in Gut Bacterial Metabolism Associate with Host Health

The metabolism of gut bacteria, that is what they eat and produce, can vary and this has a big influence on human health, such as the way we look or diseases we may develop. Gut microbiota, being all micro-organisms in the gut, is associated with diseases, but how this works is poorly known. This thesis investigates bacterial metabolisms in relation to human characteristics and their genetic make-up. To do this, we first build a platform that we call culturomics to grow faecal bacteria and used it to identify 724 bacteria from healthy volunteers, including several new and lesser-known species. Investigating these bacteria, showed for the first time that your genetic blood type that regulates the composition of gut slime determines which bacteria grow there. Furthermore, the bacteria that metabolise this slime associate with cardiometabolic health. Inositols, special sugars from our diet, are broken down by a specific group of beneficial bacteria. A test in worms showed that these inositol-fed bacteria affect host fat storage. Furthermore, we think that bacterial inositol metabolism can help to manage reduced fertility in women. Beneficial gut bacteria are often oxygen-sensitive. However, in an oxygenated gut model, the survival of these bacteria was enhanced by adding complex carbohydrates. These bacteria use riboflavin (vitamin B2) to deal with toxic oxygen and a clinical trial showed that riboflavin stimulates gut bacterial production of beneficial metabolites (butyrate). All these findings will help us understand bacterial metabolism in host-microbe interactions and develop personalized medicine for health.