N2 fixation by bacteroids. the total oxidation of malate by the citrate cycle yields five NDAH and one FADH2. The formation of two NH3 from N2 and accompanying reduction of 2H+ to H2 requires 16 molecules of ATP. Generation of this ATP by the respiratory chain localized in the bacteroid membrane requires the oxidation of about eight molecules of NADH. Thus for each molecule of N2 fixed four molecules of O2 are consumed by the oxidation of NADH in the respiratory chain of the bacteroid membrane.
 
 

To the Rhizobium-legume association