What is a holobiont in short?

The holobiont is you together with all your micro-organisms, regarded as one biological whole that digests, defends and adapts together.

Am I more bacteria than human?

You carry roughly as many microbial cells as your own cells. More important is that the microbiome contributes far more genes than your own genome, which greatly expands your metabolic possibilities.

Why does the holobiont idea matter for health?

Because health is not determined by your own genes alone, but also by which micro-organisms live with you and how you work together.

Is the holobiont scientifically accepted?

The underlying mechanisms — immune training, co-metabolism, colonisation resistance — are peer-reviewed. The precise scope of the hologenome theory remains a subject of scientific debate.

CosmoLexicon › Holobiont

Holobiont

EN: holobiont · related terms: microbiome, co-metabolism, dysbiosis

Definition A holobiont is the whole of a host — such as the human being — together with all of its micro-organisms (bacteria, viruses, fungi), regarded as one biological unit. The human and the microbiome do not function separately, but as one collaborating ecosystem that grows, digests, defends and adapts together.

In plain language

You are never entirely alone. In your gut, on your skin and in your mouth live trillions of micro-organisms, and together with you they form one working whole: the holobiont. Think of a coral reef — the coral and the algae inside it are not viable on their own, but together they form a thriving reef. It is the same with you: your cells and your microbes do things that neither could do alone. They help you digest fibre, make vitamins, train your defences and even send signals to your brain. That collaboration also means that 'health' is not only your genes, but also who is aboard with you. Once you understand yourself as a holobiont, you understand why nutrition, lifestyle and your microbes must always be looked at together.

The science behind

The holobiont concept, popularised by Lynn Margulis among others and later developed in the hologenome theory, regards host and microbiome as one unit of selection with a shared genetic potential (the hologenome). The human microbiome carries many times more genes than the human genome, which greatly expands the metabolic and immunological reach of the holobiont.

A few core mechanisms through which the holobiont functions:

• Metabolic complementarity. Micro-organisms carry out metabolic steps that the host itself lacks — think of the fermentation of fibre into short-chain fatty acids. This is the heart of co-metabolism.
• Immune training. From birth onwards the microbiome calibrates the innate and adaptive immune system, influencing tolerance and inflammatory tone.
• Barrier and colonisation resistance. A healthy microbial community occupies niches and thereby keeps pathogens in check.
• Co-development. Host and microbiome shape each other throughout life, from early colonisation to ageing.

The holobiont lens explains why identical nutrition or lifestyle has different effects in different people: the outcome depends in part on the microbial partner. That is why My InnerSelfie reads DNA, microbiome and metabolome not separately, but as one interplay. This reading is supportive and observational — not a medical diagnosis.

Related concepts

Microbiome Co-metabolism Dysbiosis Postbiotics (SCFA)Gut-organ axes

Where appropriate — support: if you want to feed your microbial partner in a targeted way, purposeful nutrition or supplementation can support the right micro-organisms. Discover the My Key Nutrients range.

Scientific references

• Lee et al. (2024), The human gut microbiome in health and disease.
• Nature, Signal Transduction & Targeted Therapy — review on the microbiota and health (s41392-022-00974-4).
• Emily Leeming, Genius Gut.

Frequently asked questions

What is a holobiont in short?: The holobiont is you together with all your micro-organisms, regarded as one biological whole that digests, defends and adapts together.
Am I more bacteria than human?: You carry roughly as many microbial cells as your own cells. More important is that the microbiome contributes far more genes than your own genome, which greatly expands your metabolic possibilities.
Why does the holobiont idea matter for health?: Because health is not determined by your own genes alone, but also by which micro-organisms live with you and how you work together.
Is the holobiont scientifically accepted?: The underlying mechanisms — immune training, co-metabolism, colonisation resistance — are peer-reviewed. The precise scope of the hologenome theory remains a subject of scientific debate.