A number of organisms, instead of using inorganic compounds as terminal electron acceptors, are able to use organic compounds to accept electrons from respiration.  Examples include:
* Fumarate reduction to succinate
* Trimethylamine N-oxide (TMAO) reduction to trimethylamine (TMA)
* Dimethyl sulfoxide (DMSO) reduction to Dimethyl sulfide (DMS)
* Reductive dechlorination
TMAO is a chemical commonly produced by fish, and when reduced to TMA produces a strong odor.  DMSO is a common marine and freshwater chemical which is also odiferous when reduced to DMS.  Reductive dechlorination is the process by which chlorinated organic compounds are reduced to form their non-chlorinated endproducts.  As chlorinated organic compounds are often important (and difficult to degrade) environmental pollutants, reductive dechlorination is an important process in bioremediation.