Chemosynthesis is one of the primary production processes by which organic compounds are synthesized from nutrients and inorganic one-carbon compounds using energy obtained from the oxidation of inorganic compounds and organic one-carbon compounds. The process consists of two main parts: energy generation by oxidation of the growth-supporting substrate and carbon fixation (assimilation). Oxidation of the growthsupporting substrate releases electrons and energy that enable the formation of the membrane electrochemical potential, the synthesis of ATP and the reduction of NAD+ . The energy stored in this way is used, among other things, for carbon fixation. Carbon in the form of CO2 is assimilated in six possible ways, while in the form of organic one-carbon compounds it can be assimilated in three different ways. There are two main groups of chemosynthetic organisms: chemolithotrophs (the source of energy and electrons are inorganic substances, and the source of carbon is CO2) and methylotrophs (organic one-carbon substances are the source of energy, electrons, and carbon). Chemosynthetic organisms can survive in different living conditions and consequently show a great diversity of metabolism regarding the type of groowth-supporting substrate, the type of terminal electron acceptor and the carbon source.