chemoheterotrophic

Chemoheterotrophy is a mode of metabolism in which an organism derives energy from the chemical oxidation of organic compounds and uses organic compounds as its carbon source. In chemoheterotrophs, both energy and carbon are obtained from organic substrates such as sugars, amino acids, and organic acids.

Energy acquisition occurs mainly through respiration or fermentation. In respiration, organic substrates are oxidized with an electron transport chain and a terminal electron acceptor, which can be oxygen or other inorganic or organic compounds. In fermentation, ATP is produced primarily by substrate-level phosphorylation without a final external electron acceptor. Chemoheterotrophs include a wide range of organisms, such as many bacteria, fungi, most protists, and all animals, and they are central to decomposition, nutrient cycling, and various ecological interactions, including pathogenesis and symbioses.

This nutritional mode is contrasted with chemoautotrophy, in which organisms obtain energy from the oxidation of inorganic compounds and fix CO2 as a carbon source. It is also distinct from photoautotrophy and photoheterotrophy, where light provides the energy source. Within chemoheterotrophy, organisms may be chemoorganotrophs, using organic electron donors, or chemolithotrophs, using inorganic electron donors (though most chemoheterotrophs are also chemoorganotrophs). Overall, chemoheterotrophy highlights the reliance on organic compounds both for energy and biomass, supporting a vast diversity of life and ecological roles.