Diatoms are extremely unique organisms. They are extremely abundant photosynthetic algae, with a few exceptions which are heterotrophic or mixatrophic. They store energy in the form of oils and they usually produce extra cellular. polysaccharides. But on top of it all they have cell walls. Their cell walls aren’t made of cellulose or peptidoglycan or any other complex organic molecule. Instead they are surrounded in a silica (glass) cell wall which is often call frustules