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Concept
Lithotroph
Résumé
Lithotrophs are a diverse group of organisms using an inorganic substrate (usually of mineral origin) to obtain reducing equivalents for use in biosynthesis (e.g., carbon dioxide fixation) or energy conservation (i.e., ATP production) via aerobic or anaerobic respiration. While lithotrophs in the broader sense include photolithotrophs like plants, chemolithotrophs are exclusively microorganisms; no known macrofauna possesses the ability to use inorganic compounds as electron sources. Macrofauna and lithotrophs can form symbiotic relationships, in which case the lithotrophs are called "prokaryotic symbionts". An example of this is chemolithotrophic bacteria in giant tube worms or plastids, which are organelles within plant cells that may have evolved from photolithotrophic cyanobacteria-like organisms. Chemolithotrophs belong to the domains Bacteria and Archaea. The term "lithotroph" was created from the Greek terms 'lithos' (rock) and 'troph' (consumer), meaning "eaters of rock". Many but not all lithoautotrophs are extremophiles.
The last universal common ancestor of life is thought to be a chemolithotroph (due to its presence in the prokaryotes). Different from a lithotroph is an organotroph, an organism which obtains its reducing agents from the catabolism of organic compounds.
The term was suggested in 1946 by Lwoff and collaborators.
Lithotrophs consume reduced inorganic compounds (electron donors).
A chemolithotroph is able to use inorganic reduced compounds in its energy-producing reactions. This process involves the oxidation of inorganic compounds coupled to ATP synthesis. The majority of chemolithotrophs are chemolithoautotrophs, able to fix carbon dioxide (CO2) through the Calvin cycle, a metabolic pathway in which CO2 is converted to glucose. This group of organisms includes sulfur oxidizers, nitrifying bacteria, iron oxidizers, and hydrogen oxidizers.
The term "chemolithotrophy" refers to a cell's acquisition of energy from the oxidation of inorganic compounds, also known as electron donors.
Source officielle
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