The community of microorganisms and their collective genetic material inhabiting a particular environment, such as the human gut or soil.
Explanation
The term “microbiome” refers to the entire collection of microbes—bacteria, archaea, fungi, protozoa and viruses—and their genes in a defined habitat. Coined in the late twentieth century, the word highlights that microbial communities form integrated systems with functional genomes. It is often used interchangeably with “microbiota”, though microbiome emphasises the combined genetic repertoire. Advances in DNA sequencing and bioinformatics have enabled researchers to characterize microbiomes without culturing organisms, revealing thousands of previously unknown lineages. Within the human body, distinct microbiomes exist on the skin, in the oral cavity, gut, respiratory tract and urogenital tract, each shaped by factors such as diet, age, hormones and environment. These resident microbes play vital roles in digestion, metabolism, immune system development and protection against pathogens.
Microbiome composition is dynamic and can change in response to antibiotics, infection or dietary shifts. Disruption of a balanced microbial community—termed dysbiosis—has been associated with conditions ranging from inflammatory bowel disease and obesity to allergies and neurodevelopmental disorders. Because microbiomes influence host physiology, they are a focus of research aimed at developing microbiome ‑based therapies, including probiotics, prebiotics and faecal microbiota transplantation. Environmental microbiomes, such as those in soil and oceans, are also critical for nutrient cycling and ecosystem stability. Understanding the structure and function of microbiomes provides insight into the interconnectedness of life at the microscopic level.
Examples and Health Implications
The human gut microbiome contains trillions of bacteria, dominated by the phyla Firmicutes and Bacteroidetes. These microbes ferment dietary fibres into short‑chain fatty acids, synthesize vitamins and modulate the immune response. The vaginal microbiome of reproductive‑age women is typically dominated by Lactobacillus species, which produce lactic acid to maintain a low pH and prevent overgrowth of pathogenic bacteria. On the skin, commensal microbes such as Staphylococcus epidermidis inhibit colonization by pathogens. In agriculture, the rhizosphere microbiome surrounding plant roots enhances nutrient uptake and provides resistance to pathogens. Studies of the oral microbiome help elucidate causes of dental caries and periodontitis.
Microbiome research is reshaping our understanding of health and disease. Strategies to manipulate microbial communities aim to restore balance after dysbiosis or enhance beneficial functions. Continued exploration of microbiomes across diverse environments promises to reveal new metabolic capabilities and ecological interactions.
Related Terms: Microbiota, Metagenomics, Dysbiosis, Human gut, Symbiosis