A lithoautotroph is an organism that derives energy from reactions of reduced compounds of mineral (inorganic) origin. Two types of lithoautotrophs are distinguished by their energy source; photolithoautotrophs derive their energy from light, while chemolithoautotrophs (chemolithotrophs or chemoautotrophs) derive their energy from chemical reactions. Chemolithoautotrophs are exclusively microbes. Photolithoautotrophs include macroflora such as plants; these do not possess the ability to use mineral sources of reduced compounds for energy. Most chemolithoautotrophs belong to the domain Bacteria, while some belong to the domain Archaea. Lithoautotrophic bacteria can only use inorganic molecules as substrates in their energy-releasing reactions. The term "lithotroph" is from Greek lithos (λίθος) meaning "rock" and trōphos (τροφοσ) meaning "consumer"; literally, it may be read "eaters of rock." The "lithotroph" part of the name refers to the fact that these organisms use inorganic elements/compounds as their electron source, while the "autotroph" part of the name refers to their carbon source being CO2. Many lithoautotrophs are extremophiles, but this is not universally so, and some can be found to be the cause of acid mine drainage.
Lithoautotrophs are extremely specific in their source of reduced compounds. Thus, despite the diversity in using inorganic compounds that lithoautotrophs exhibit as a group, one particular lithoautotroph would use only one type of inorganic molecule to get its energy. A chemolithotrophic example is anaerobic ammonia oxidizing bacteria (anammox), which use ammonia and nitrite to produce dinitrogen (N2). Additionally, in July 2020, researchers reported the discovery of chemolithoautotrophic bacterial cultures that feed on the metal manganese after performing unrelated experiments and named their bacterial species Candidatus Manganitrophus noduliformans and Ramlibacter lithotrophicus.
