The human microbiome is like an invisible world living alongside us everyday. It’s made up of trillions of tiny organisms such as bacteria, fungi, viruses, and many more that call our bodies home. Even though we can’t see them, they play a huge role in how we digest food, fight off illness, and even how we feel emotionally. Each person’s microbiome is completely unique, shaped by factors like genetics, lifestyle, and the foods we eat.

Bacteria are prokaryotic organisms (that are composed of only one cell) that can reproduce really fast and adapt to many environments. There are two kingdoms of bacteria: Eubacteria, which are the “true” bacteria, and the Archaebacteria, which are the oldest organisms on Earth and live in extreme conditions. They can be aerobic or anaerobic, depending on the surroundings and the presence of oxygen. In the human gut they are able to help the digestion of food, production of vitamins, and the protection against harmful pathogens.

Among the many microbes that support us, one standout is Bacteroides thetaiotaomicron. This helpful gut bacterium specializes in breaking down tough plant fibers we wouldn’t be able to digest on our own. In doing so, it creates short-chain fatty acids that help fuel our gut cells, calm inflammation, and support a healthy metabolism. It also adapts to whatever we eat, making it a steady partner in keeping our digestive system running smoothly.

Most microbiome research focuses on the gut, and for good reason. The microbes living there help produce vitamins, guide our immune system, and influence everything from our weight to our risk for certain diseases.