A mixotrophic organism is one that obtains its electrons from an inorganic electron source (hydrogen-sulfide, ammonium, hydrogen), but uses organic matter as a carbon source. Some of these organisms are facultative chemolithotrophs or facultative chemoorganotrophs, and are capable of using either metabolism depending on environmental conditions. Also, some of these organisms have incomplete Calvin cycles, so they are incapable of fixing carbon dioxide and must use organic carbon sources. An example of a mixotrophic organism would be Beggiatoa.
