Microbiome

A vocabulary nuance that is often confused:

• Microbiota: the community of micro-organisms themselves (the bacteria, viruses and fungi)
• Microbiome: the broader whole that includes these micro-organisms AND their collective genetic heritage, their metabolites and their environment

In practice, the two terms are often used interchangeably, but “microbiome” stresses the genetic and functional dimension.

The original angle (our second genome): a dizzying figure: the gut microbiome contains about 150 times more genes than the human genome! It is sometimes called a “second genome“. These bacterial genes code for functions that our own DNA lacks: breaking down certain fibres, synthesising vitamins (K and some B vitamins), producing neurotransmitters, and metabolising medicines and polyphenols.

In other words, our real metabolic capacities are a partnership between our genes and those of our bacteria. Two people with the same human genome but different microbiomes “digest” and react differently to the same foods.

Microbial individuality: every microbiome is unique, more personal than a fingerprint. It depends on birth (vaginal delivery vs caesarean), breastfeeding, diet, environment, antibiotics and lifestyle. This uniqueness explains why personalised nutrition is emerging: the same food causes different blood sugar responses depending on the microbiome (Zeevi/Segal study, Cell, 2015).

Implications for the future: the microbiome opens up new prospects: personalised nutrition based on your bacterial profile, faecal microbiota transplantation (already effective against some infections), psychobiotics, and targeting of specific bacteria. It is a major frontier in medicine and nutrition.

Feeding it: dietary diversity (each fibre feeds different bacteria), fermented foods, fibre and prebiotics, and limiting ultra-processed foods and unnecessary antibiotics.