1) Characteristic microbial community occupying a reasonably well-defined habitat which has distinct physio-chemical properties. It not only refers to the microorganisms involved but also encompass their theatre of activity, which results in the formation of specific ecological niches. 2) Ecological community of commensal, symbiotic, and pathogenic microorganisms within a body space. Source: Microbiome definition re-visited (2020) [https://doi.org/10.1186/s40168-020-00875-0]