Biotechnology of extremophiles

An extremophile is an organism living in an extreme environment. What is an extreme environment? Answers to this simple question have varied from one era to the next. First of all, we were talking about environments hostile to man, where human life seemed impossible. This anthropocentric conception gave way to an approach based on the observation of macroscopic life forms. Then, in the second half of the 20th century, the inventory of life forms led to the discovery of micro-organisms living in increasingly unlikely environments previously considered sterile: hot springs, hydrothermal springs, acidic, alkaline and hypersaline lakes, deep marine sediments, oil reservoirs, glaciers and so on. These discoveries have progressively pushed back the known physical and chemical limits of life on Earth. To this day, certain limits remain undefined, and research continues to define the boundaries of the biosphere. This is particularly the case for micro-organisms in the deep sediments of the ocean floor (subsurface biosphere) and for the limits of life under pressure. These discoveries have also led to the revision of hypotheses about life on other planets (exobiology).

Over the course of evolution, organisms living in extreme environments, and micro-organisms in particular, have developed a wide variety of adaptive strategies. As a result, they have developed a repertoire of metabolic pathways and original biomolecules that enable them not only to survive in extreme conditions, but also to develop, often optimally, in extreme ecological niches. The singular properties of some of these biomolecules quickly attracted the attention of biotechnology operators: researchers, engineers and companies. The aim of extremophile biotechnology is to seek out and exploit this new source of natural biomolecule resources, in particular enzymes, biopolymers and secondary metabolites. Since nature and evolution have generated an extensive repertoire of biomolecules, it seems logical to draw on this repertoire when the properties of a biomolecule meet the specifications of a biotechnological application. If only partial adaptation to the specifications is achieved, the biomolecule can nevertheless serve as the starting point for an engineering process aimed at improving its performance, or as a model for the chemical synthesis of high-performance products.