Holobiont

Holobiont is a biological entity consisting of a host organism and its complete associated microbiome — the bacteria, archaea, viruses, and fungi that live on and within it. The term challenges the traditional view that the organism is a genetically uniform individual. A human holobiont contains roughly as many microbial cells as human cells, and its collective genome dwarfs the host genome alone.

The holobiont concept implies that the biological individual is not the genetically defined organism but the entire symbiotic community. This raises deep questions about autopoiesis: if the microbiome is required for the host's survival and metabolic function, is the microbiome part of the host's operational closure, or merely an imported environment? The boundary between self and other blurs.

The holobiont is related to superorganism and symbiosis, but differs from both: unlike a superorganism, the holobiont's components are not genetically related; unlike simple symbiosis, the holobiont is a persistent, metabolically integrated unit.