 Anaerobic bacteria such as "Clostridium acetobutylicum" and "Clostridium saccharobutylicum" also contain these pathways.Succinate is first activated and then reduced by a two-step reaction to give 4-hydroxybutyrate, which is then metabolized further to crotonyl-coenzyme A (CoA) .Crotonyl-CoA is then converted to butyrate.