microorganism vs germ

microorganism and germ both are nouns.

Word	Noun	Adjective	Verb	Adverb
microorganism	Yes	No	No	No
germ	Yes	No	No	No

As nouns, germ is a hyponym of microorganism; that is, germ is a word with a more specific, narrower meaning than microorganism:

microorganism: any organism of microscopic size
germ: a minute life form (especially a disease-causing bacterium); the term is not in technical use

microorganism (noun)	germ (noun)
any organism of microscopic size	a minute life form (especially a disease-causing bacterium); the term is not in technical use
	a small apparently simple structure (as a fertilized egg) from which new tissue can develop into a complete organism
	anything that provides inspiration for later work