Inclusion bodies: Reserve material in prokaryotic cells are stored in the cytoplasm in the form of inclusion bodies. These are not bounded by any membrane system and lie free in the cytoplasm, e.g., phosphate granules, cyanophycean granules, and glycogen granules. Some other inclusion bodies may be surrounded by a single layer non-unit membrane, which is 2-4 nm thick. e.g.-poly-$\beta$-hydroxybutyrate granules, sulphur granules, and gas vacuole. Gas vacuoles are found in blue-green algae, purple and green photosynthetic bacteria.