LAUSR

One of the hallmarks of all living beings is their ability to extract energy from their surroundings and use it in a process termed metabolism to grow and reproduce. During evolution, life had to "learn" how to cope with changing environments and exploit even limited and unstable sources of energy. The ability to take up and process energy from diverse sources and adjust their metabolism according to the availability of nutrients is therefore fundamentally engrained in the nature of all living things. This holds true for singlecelled microorganisms that need to survive in competitive environments as well as for multicellular organisms such as plants and animals whose cells need to function within the context of tissues. With increasing complexity organisms have evolved more and more intricate networks of enzymes and cofactors that interconvert metabolites in order to satisfy their need for energy and to provide chemical building blocks. The biochemical reactions that take place in cells are based on the versatility of carbon chemistry. The carbon source is therefore at the center of an organism’s metabolism and determines the modes of energy and biomass production. Being able to produce their own energy and building materials, autotrophic organisms have often evolved to be immobile or incapable of active migration. As such, they have to cope with their immediate surroundings, and they need to be able to withstand fluctuations in e.g. light, temperature, and water availability, and to adapt to the conditions in their habitat. Therefore, for autotrophic organisms, adaption of their metabolism to the environment is of major importance. Heterotrophic organisms, on the other hand, have evolved means to sense nutrients, and they have adaptions that allow them to get to, capture, and digest food stuffs. Their metabolic circuitries have evolved to be able to deal with different types and changing amounts of food. The information for how, when, and where to make the enzymes that are required for adenosine triphosphate (ATP) production and the synthesis of biomolecules is encoded in an organism’s genome. All