The terms ‘microbiome’ and ‘microbiota’ are used interchangeably—especially in the media—but their meanings are subtly different:4
Microbiota is the collection of all microbial taxa in a specific community. This can include bacteria, archaea, fungi and protozoa and more. The community is linked to its environment i.e. ‘gut microbiota’ or ‘oral microbiota’.
Microbiome indicates the genes harboured by all the microbes in a specific environment.
So, microbiota refers to the microbes, while microbiome refers to their genes. To understand this, picture a group of humans. The collection of humans would be the microbiota, while the total DNA of all the humans would be the microbiome.
Because we discover new microbes by looking at their genes, ‘microbiome’ is the buzzword that’s stuck. And what we’ve found so far has been staggering:
There are 22,000 genes in the human microbiome. To date, we know of 3.3 million genes in the gut microbiome alone.5
Humans are about 99.9% genetically identical to each other. But people can be 80–90% different from one another in terms of their gut microbiome.6
Clearly, these microbes matter.