Unclassified Bacteria, Fungi and Virus

Some people get concerned about finding unclassified stuff in their microbiome sample. This does not happen with some labs because they elected not to report what is not classified. Why? It leads to support calls asking for explanations (which means $$$$ spent for the company).

Labs could create synthetic proprietary names for the unclassified to make the issue disappear — that causes the issue to disappear but really does not help.

There is a part 2: Different Microbiome Results from Different Providers on Same Sample

An Analogy

Bacteria is like the population of a country or the world. They interbred to some extent

Genetic exchanges among bacteria occur by several mechanisms. In transformation, the recipient bacterium takes up extracellular donor DNA. In transduction, donor DNA packaged in a bacteriophage infects the recipient bacterium. In conjugation, the donor bacterium transfers DNA to the recipient by mating.

Medical Microbiology. 4th edition., Chapter 5

So doing a microbiome test is like collecting the DNA from a bunch of people at a major airport and then asking: Which country did this person originated from according to their DNA. You will find some people that are good matches to an ethnic origin and some people that are “Heinz 57” aka “Mutts”. These people are unclassified — just like some living components are unclassified.

If I was picked, the answer is pretty clear for the “genus” that fits me

Which agrees with paper records back to 1500

If we want to get a more precise name, the “species”, then some fuzziness appears

There is a possible misidentification, my father’s ancestors (all lines) records go back to 1600 on an island that is low probability.


The process of giving names to bacteria in the microbiome is extremely similar. For some bacteria (like me) we fit into a nice box. For the person below, the box is not so clear

Would this person be classified as Irish or English

Bottom Line

A wise man knows what he does not know, and what cannot be known.

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