A given condition is considered extreme, when most organisms are not able to survive in it. Some extremophiles can grow at suffocating temperatures, insane pHs, salt concentrations that should be sterilizing, high pressures … They are mainly bacteria and archaea and they are challenging the limits of life (as we know it today).
Life under these conditions implies, without doubt, the development of unique physiological characteristics, phenotypic properties and adaptive mechanisms. As we mentioned before, all cells share essential macromolecules such as nucleic acids and proteins. In order to fulfill their functions, these macromolecules must fold correctly (take an appropriate three-dimensional structure). And for the adequate folding, liquid water plays a crucial role (hence the fact that when we look for habitable exoplanets, the requirement sine qua non is the presence of liquid water). In harsh conditions, the properties of water change and become limiting. It is precisely here where the existence of extremophiles becomes interesting, how do they cope with it? Without going into detail, these organisms understood it perfectly well and they have developed strategies to maintain (i) the liquid water and its physico-chemical properties and (ii) the chemical bonds of its macromolecules. They are amazing, right? Which one is your favorite?