Rhizobia is a bacteria that infects some plants, namely legumes. Once the plant is infected, nodules (bumps) form within the roots of the host plant converting nitrogen gas from the air into ammonium…most of the ammonium is passed onto the plant so it takes the place of nitrogen to store meanwhile the bacteria take carbon from the plant to continue forming “nitrogen balls” living in symbiosis…it is this bacteria that fixes nitrogen not the plant.
As far as I know rhizobia is picky for its host preferring beans, alfalfa, peas and clover only. Now there are a couple other bacteria related to rhizobia though they do not form the symbiotic relationship to actually fix the nitrogen from the air into the soil…I am sure there is a study on it somewhere