Microbiome
The collective community of microorganisms — bacteria, archaea, fungi, viruses — living on and in a host organism.
The microbiome is the entire community of microorganisms living in or on a particular environment, most commonly used to refer to the human body. The human gut alone hosts an estimated 10-100 trillion microbes, collectively about 1-2 kg of biomass and outnumbering human cells.
Microbiomes contribute to digestion (especially of fibres), train the immune system, synthesise vitamins, help exclude pathogens, and may influence mood through the gut-brain axis. Disruptions are associated with numerous conditions including inflammatory bowel disease and possibly obesity, autoimmune disorders, and depression.
Diet, antibiotics, age, stress, and lifestyle all reshape the microbiome — sometimes within days. Diverse, fibre-rich whole-food diets are the best-evidenced way to support a healthy microbiome.