Chemoorganoheterotrophs (or simply organotrophs) exploit reduced carbon compounds as energy sources, such as carbohydrates, fats, and proteins from plants and animals. Chemolithoheterotrophs (or lithotrophic heterotrophs) such as colorless sulfur bacteria (e.g., Beggiatoa and Thiobacillus) and sulfate-reducing bacteria utilize inorganic substances to produce ATP, including hydrogen sulfide, elemental sulfur, thiosulfate, and molecular hydrogen.[2][3][4][5] They use organic compounds to build structures. They do not fix carbon dioxide and apparently do not have the Calvin cycle.[2] Chemolithoheterotrophs can be distinguished from mixotrophs (or facultative chemolithotroph), which can utilize either carbon dioxide or organic carbon as the carbon source.[3][6] Heterotrophs, by consuming reduced carbon compounds, are able to use all the energy that they obtain from food for growth and reproduction, unlike autotrophs, which must use some of their energy for carbon fixation. Heterotrophs are unable to make their own food, however, and whether using organic or inorganic energy sources, they can die from a lack of food. This applies not only to animals and fungi but also to bacteria An organotroph is an organism that obtains hydrogen or electrons from organic substrates. This term is used in microbiology to classify and describe organisms based on how they obtain electrons for their respiration processes. Some organotrophs such as animals and many bacteria, are also heterotrophs. Organotrophs can be either anaerobic or aerobic A mixotroph is an organism that can use a mix of different sources of energy and carbon. Possible are alternations between photo- and chemotrophy, between litho- and organotrophy, between auto- and heterotrophy or a combination of it. Mixotrophs can be either eukaryotic or prokaryotic.[1] They can take advantage of different environmental conditions.[2] If a trophic mode is obligate, then it is always necessary for sustaining growth and maintenance; if facultative, it can be used as a supplemental source.[1] Some organisms have incomplete Calvin cycles, so they are incapable of fixing carbon dioxide and must use organic carbon sources. Examples Paracoccus pantotrophus is a bacterium that can live as chemoorganoheterotroph, whereby a large variety of organic compounds can be metabolized. Also a facultative chemolithoautotrophic metabolism is possible, as seen in colorless sulfur bacteria (some Thiobacillus), whereby sulfur compounds such as hydrogen sulfide, elemental sulfur, or thiosulfate are oxidized to sulfate. The sulfur compounds serve as electron donors and are consumed to produce ATP. The carbon source for these organisms can be carbon dioxide (autotrophy) or organic carbon (heterotrophy).[3][4][5] Organoheterotrophy can occur under aerobic or under anaerobic conditions; lithoautotrophy takes place aerobically.[6][7] Many examples of the genus Euglena. Oriental hornet Vespa orientalis Venus Flytrap Dionaea muscipula