Anaerobic Cellular Respiration

Anaerobic cellular respiration is similar to aerobic cellular respiration in that electrons extracted from a fuel molecule are passed through an electron transport chain, driving synthesis. Some organisms use sulfate (SO4) as the final electron acceptor at the end ot the transport chain, while others use nitrate (NO3), sulfur, or one of a variety of other molecules.
What kinds of organisms use anaerobic cellular respiration? Some prokaryotes — bacteria and archaea — that live in low-oxygen environments rely on anaerobic respiration to break down fuels. For example, some archaea called methanogens can use carbon dioxide as a terminal electron acceptor, producing methane as a by-product. Methanogens are found in soil and in the digestive systems of ruminants, a group of animals including cows and sheep.
Similarly, sulfate-reducing bacteria and Archaea use sulfate as a terminal electron acceptor, producing hydrogen sulfide (H2S) as a byproduct. 
https://www.khanacademy.org/science/ap-biology/cellular-energetics/cellular-respiration-ap/a/fermentation-and-anaerobic-respiration

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