Chemotroph



Chemotrophs are organisms that obtain energy by the oxidation of electron donating molecules in their environments. These molecules can be organic (organotrophs) or inorganic (lithotrophs). The chemotroph designation is in contrast to phototrophs which utilize solar energy. Chemotrophs can be either autotrophic or heterotrophic.
 * Chemoautotrophs (or chemotrophic autotroph), in addition to deriving energy from chemical reactions, synthesize all necessary organic compounds from carbon dioxide. Chemoautotrophs generally only use inorganic energy sources. Most are bacteria or archaea that live in hostile environments such as deep sea vents and are the primary producers in such ecosystems. Evolutionary scientists believe that the first organisms to inhabit Earth were chemoautotrophs that produced oxygen as a by-product and later evolved into both aerobic, animal-like organisms and photosynthetic, plant-like organisms. Chemoautotrophs generally fall into several groups: methanogens, halophiles, sulfur reducers, nitrifiers, anammoxbacteria and thermoacidophiles.
 * Chemoheterotrophs (or chemotrophic heterotrophs) must ingest organic building blocks that they are incapable of creating on their own. Most chemoheterotrophs derive energy from organic molecules like glucose.

The names of these primary nutritional groups are built from Greek roots. "Chemo" means "chemical" and "troph" means "nourishment". "Auto" means "self" and "hetero" means "other".