A possible mechanism of how stress controller bacteria reduce ethylene levels in the plant root using bacterial ACC deaminase. ACC synthesized in plant tissues by ACC synthase is thought be exuded from plant roots and be taken up by neighboring bacteria. Subsequently, the bacteria hydrolyze ACC to ammonia and 2-oxobutanoate. This ACC hydrolysis maintains ACC concentrations low in bacteria and permits continuous ACC transfer from plant roots to bacteria. Otherwise, ethylene can be produced from ACC and then cause stress responses including growth inhibition. S-AdoMet: S-adenosyl-l-methionine; ACC: 1-aminocyclopropane-1-carboxylate (Adapted from Kang et al. (2010)).