The evolution of the gut microbiota, over time. Red represents the microbial phylogenetic tree after 5 days of colonisation; orange, the tree after 20 days of colonisation; and yellow represents the microbial ecosystem of a conventional mouse.
Even though we know a great deal about the human body, we are often surprised by new discoveries. When it comes to the ‘gut flora’ – microorganisms that live in the gut – do you know that somewhere between 300-1000 different ones live in the human gut? As soon as an infant is born, bacteria begin to colonize his or her digestive tract.
Recent research by Dr. Sandrine Claus, metabonomics lecturer at the Department of Food & Nutritional Sciences at the University of Reading, UK, and her team offers insights into the crucial relationship between the host body and its gut microbes, known as microbiota.
Escherichia coli: One of the many species of bacteria present in the human gut.
In a brief interview, Dr. Claus spoke with Environmental Graffiti about her new research and let us know more about it in her own words.
EG: Kindly explain the relationship between the body and gut microbes.
Dr. Sandrine Claus: The relationship between the host and its gut microbiota is very complex and is still a considerable area of research; even if we know that they influence each other, the exact mechanisms of interaction are still poorly understood. The most obvious role of the gut microbiota is to help digestion and produce essential vitamins for the host. Not only do they provide nutrients for the host, but they also influence the normal development of the gut and stimulate the immune system. For example, germ-free animals display many gastrointestinal morphological abnormalities such as an underdeveloped intestinal membrane and they present a “naïve” immune system.
On the other hand, we also know that changing the diet has a strong impact on the gut flora, and it is thus possible to influence the composition of the gut microbial ecosystem.
Gut microbiota establishment
EG: How can changing the internal microbial environment, known as the microbiota, impact health?
SC: Influencing the gut microbial ecosystem can have a protective effect against opportunistic pathogens, i.e. bacteria normally present in the healthy gut but which may become harmful when the immune system is degraded. By facilitating the growth of protective bacteria that will compete against the opportunistic pathogens for food and adhesion sites to the intestinal membrane, they can prevent the pathogens entering the body.
Another aspect of the potential benefit of modifying the gut microbiota is to influence the absorption of some nutrients, such as lipids. In the future, we hope that we will be able to “shape” the microbial ecosystem to prevent some metabolic diseases such as obesity or diabetes.
Anatomy of liver and gall bladder
EG: How does a bacterium exert some level of control over the actual functions of organs, including the liver?
SC: In the paper published in mBio in March, we found that the colonisation of the gastrointestinal tract influences the metabolism of many organs, including the liver. These perturbations affected the metabolism of glucose (glycogenesis) followed by modifications of the lipid (triglyceride) metabolism. Concomitantly, the endogenous metabolism of drug-detoxification was stimulated.
At the same time, we observed strong modulations of the metabolism of bile acids (in the liver) which are known to influence glucose and lipid metabolism. At this stage, we observed distinct mechanisms which suggest the involvement of bile acids but no experience has clearly linked these phenomena together to demonstrate how the bacteria actually play a role on the hepatic metabolism. Some colleagues at Washington University in Saint Louis have demonstrated a role of the gut bacteria on lipid transport, which is also an element of the complex interaction between gut bacteria and the host lipid metabolism.
EG: Recently, scientists found that gut bacteria may influence mammalian brain development and adult behavior. What is your opinion on the same?
SC: This study is fascinating! I read it when it came out with a lot of attention. It demonstrates clearly that the influence of the gut microbiota extends beyond local interactions and has a systemic effect on the whole organism.
My sincere thanks to Dr. Sandrine Claus for her answers and sharing important information about her research work with us.