chemosynthesis
————————————————Chemosynthesis is the conversion of carbon compounds and other molecules into organic compounds. In this biochemical reaction, methane or an inorganic compound, such as hydrogen sulfide or hydrogen gas, is oxidized to act as the energy source. In contrast, the energy source for photosynthesis (the set of reactions through which carbon dioxide and water are converted into glucose and oxygen) uses energy from sunlight to power the process.
https://www.thoughtco.com/chemosynthesis-definition-and-examples-4122301
https://www.sciencedaily.com/releases/2016/04/160415125954.htm
“New light has been shed on a curious group of bacteria that use iron in much the same way that animals use oxygen: to soak up electrons during biochemical reactions. When organisms — whether bacteria or animal — oxidize carbohydrates, electrons must go somewhere.”