Microbiota as an Organ. Is it an Intermediate Step in Evolution?

The Origin of Mitochondria: 1.500 million years ago, a prokaryotic cell with the ability to obtain energy using molecular oxygen, fused with another prokaryotic cell (or primitive eukaryotic). It was phagocytized without being immediately digested. This is how a permanent symbiosis was built between both beings: the absorbed prokaryotic provided energy and, in return, the host cell supplied a stable and generous habitat in which it could live.

The text above briefly describes the well-known endosymbiotic theory of the Origin of Mitochondria, and it serves as a preface for the little fiction tale below.

We hope you like it!

1.000 million years have passed from the end of World War II and humans have now succeeded in inhabiting almost all of the known universe.

In a small laboratory located in Mars, the Ukrainian scientific Roman Metchnikoff, a (very) distant relative of the Nobel Price Élie Metchnikoff, researches small organelles in the cells of the human intestinal epithelium.

These small organelles are almost fused with the enterocyte membrane and they have channels which transport big molecules of fibre, like inulin or resistant starch to its interior. Several enzymatic mechanisms produce large amounts of short chain fatty acids, such as butyric acid. These nutrients represent an essential source of energy for the organism.

Over hundreds of millions of years humans have gradually changed their dietary habits, from an almost absence of fibre (at the end of the 21st century) to ‘nowadays’ where, quantitatively speaking, fibre represents around 50% of the caloric intake.

Our good friend Roman is asking himself many questions… What is the origin of these little organelles which highly produce short chain fatty acids? Are they related to the changes in dietary habits that have occurred in the last million years?

Amongst the articles he reads from the 21st century, he discovers that the scientific community was researching about something called ‘microbiota’, which they were beginning to call another ‘organ’ of the human body. They defined it as a group of microorganisms which lived in symbiosis with the body, living mainly in the openings to exterior cavities such as the digestive system…

The research that Roman has uncovered reveals further articles that describe the main functions of the bacteria of the intestinal microbiota. One of them was the production of short chain fatty acids, which served as an energy substrate for the cells of the intestinal epithelium… and suddenly he thinks, what if somehow these bacteria were absorbed into the actual intestinal cell of the intestinal epithelium?

Years later, Roman proudly follows the steps of a his ancestor and earns the Nobel Prize because  of his research entitled: ‘The Endosymbiotic Theory about the Extinction of the Intestinal Microbiota’

To be continued…

We hope you have enjoyed our little story… but what if the fiction wasn’t that far away from a future reality?

Currently microbiota is considered as ‘another organ’ but is this the most accurate way to conceptualise it?

What if we think about consider it another part of every organ?

Wouldn’t it be more accurate to consider the microorganisms which inhabit the surface of the digestive system as a constituent part of the system itself? The functions of these microorganisms are mainly nutritive, metabolic and immunising – and these functions are supplementary and intrinsic to the digestive system. For now these bacteria and microorganisms still live ‘above’ our cells, but who knows if the countdown has began to an evolutionary change… from symbiosis to endosymbiosis.

With this article we are exploring whether we should keep thinking about microbiota as ‘another organ’ or, rather as a constituent part of the tissues and organs they inhabit.

We wish you a great day and, of course, your comments are very welcome!



David Manrique @ManriqueDVD 

María Eugenia González @EuNutricion