Peptidoglycan is the material found in the bacterial that forms a molecular basis of the Gram stain.
_organelles
_cell wall
_nucleus

That is a big answer. ^ but yeah its cell wall.

explanation:

b,bacteria convert nitrates

into nitrogen gas.

d,plants and animals take in

and use nitrogen compounds.

e,bacteria break down waste    

products and return nitrogen  

to the soil.

a,bacteria convert atmospheric

nitrogen to ammonia.

c,bacteria convert ammonia

to nitrites and nitrates.