Question: How similar are microorganisms in 2 completly different people?

Laura Nolan answered on 7 Jan 2019:

This is a great question. Bacteria are important components within our guts and on our skin, nose and belly button (they are called commensals ie they live there all the time). In these areas the bacteria that live there are not harmful to us (ie not pathogenic) and are considered to be necessary for fighting off harmful bacteria from inhabiting these different areas of our bodies. The bacteria which live in these different areas are specialised to grow and survive under the particular environmental conditions in that area eg. to be able to survive in low/no oxygen and low pH in the gut and to be able to grow in dry, high salt conditions on our skin. On the skin, nose and belly button most people have the same kinds of bacteria, no matter where they live, what their diet is and whether they are healthy or ill. However, the guts of two different people can have very different kinds of bacteria which can influence whether one person might be more healthy and another be sick. For instance the presence of certain kinds of bacteria has been associated with a person having more issues with allergies, obesity, diabetes and gut inflammatory issues such as Crohn’s disease and coeliac disease.