nitrobacteria vs eubacterium

nitrobacteria and eubacterium both are nouns.

Word	Noun	Adjective	Verb	Adverb
nitrobacteria	Yes	No	No	No
eubacterium	Yes	No	No	No

As nouns, eubacterium is a hypernym of nitrobacteria; that is, eubacterium is a word with a broader meaning than nitrobacteria:

nitrobacteria: soil bacteria that convert nitrites to nitrates
eubacterium: a large group of bacteria having rigid cell walls; motile types have flagella

Other hypernyms of nitrobacteria include eubacteria, true bacteria.

nitrobacteria (noun)	eubacterium (noun)
soil bacteria that convert nitrites to nitrates	a large group of bacteria having rigid cell walls; motile types have flagella