These bacteria are part of an ancestral lineage, the actinobacteria, which have a genome with a high cytosine and guanine content, enabling them to withstand extreme environmental conditions. Mycobacteria also have an outer membrane rich in mycolic acids, which makes them even more resistant. Thanks to these characteristics, mycobacteria can withstand long periods of drought and very large temperature gradients, allowing them to “wait” for spring. As the snow melts, they multiply again in the context of the high mountain plant communities, in particular the crumbs.
The particularity of their outer membrane means that when they come into contact with the intestinal mucosa they can stimulate an immunoregulatory response beneficial to human physiology. Part of the “Old Friends” group is Professor Graham Rook of University College London. Professor Rook defends the Biodiversity hypothesis, in which the microbiota of the environment is crucial for the regulation of the immune system and for avoiding the risk of chronic inflammatory disorders. This is linked to the “hygiene hypothesis“, marked by the cleanliness that surrounds us, linked to modern life and the absence of the natural stimuli by which our immune system was designed. In the absence of these stimuli, our immunity is directed against our tissues and generates autoimmune phenomena marked by a chronically increased inflammatory response.
Mycobacteria are a type of bacteria with which we have virtually no contact, because they are generated in natural sites that are shrinking as a result of climate change, environmental pollution and industrialisation. This aggression against the environment is causing the disappearance of unique areas of high mountain plant diversity such as the molleras, where mycobacteria find their best environment in which to develop.