The microbiome refers to a community of microorganisms, including bacteria, fungi, protists, algae, and archaea, that inhabit a defined environment such as the human body, animals, plants, soils, or water. It encompasses both the living microbiota and the environmental conditions around them (e.g., structural elements, metabolites, mobile genetic elements). Interactions between microorganisms and their host are essential for ecosystem functioning and host health.
Human-associated microbiomes contribute to key biological functions, including metabolism, immune regulation, and protection against pathogens. The community compositions vary across body sites (e.g., the gut, skin, or respiratory tract) and are shaped by factors such as age, diet, lifestyle, environment, and medical treatments. Disruptions to the microbiome, often referred to as dysbiosis, have been associated with a wide range of health conditions. Advances in sequencing technologies and microbial ecology are deepening our understanding of how microbiomes influence human health and disease and how they may be targeted for therapeutic or preventive interventions.