There are trillions of them – millions fitting through the eye of a needle – and they are everywhere. They live and thrive in vast communities in the environment, such as soil, rivers and oceans, and atmosphere, and in the human body. But they also exist in the oddest of places, such as extreme environments like volcanic hot springs and long-frozen ice in the Arctic.
Invisible to the human eye, they are communities of microorganisms, archaea (Greek for “ancient things”), fungi and viruses. Each community, or microbiome, can be thought of as an individual metropolis, each as different as New York City is from Albuquerque.
What’s fascinating about microbiomes is how they contribute to the “big” world. For example, various types of microbiomes thrive in the human body. Those in the human stomach help the gut absorb nutrients and minerals, as well as synthesize vitamins, enzymes (to help with digestion, among other things) and amino acids (the building blocks of proteins). This microbiome also helps train the body’s immune system battle tiny invaders, such as bacteria and viruses.