Alternative terminal electron acceptors for R. rubrum include dimethyl sulfoxide or trimethylamine oxide.

R. rubrum is also a nitrogen fixing bacterium, i.e., it can express and regulate nitrogenase, a protein complex that can catalyse the conversion of atmospheric dinitrogen into ammonia.

When the bacteria are exposed to ammonia, darkness, and phenazine methosulfate, nitrogen fixation stops.

[3] Due to this important property, R. rubrum has been the test subject of many different groups, so as to understand the complex regulatory schemes required for this reaction to occur.

Nitrogenase is modified by an ADP-ribosylation in the arginine residue 101 (Arg101)[8] in response to the so-called "switch-off" effectors - glutamine or ammonia - and darkness.