Bacterial cell. Illustration of a typical bacterial cell, sectioned to reveal its internal structures. Bacteria are prokaryotes, simple organisms without a nuclear membrane or membrane- bound organelles. The outermost layers shown here are the capsule (green) with long thin flagellae (pink). Both these structures are only present in some species. The next layers are the cell wall (blue) and the cytoplasmic membrane (orange). Intracellular inclusions (brown) are shown in the cytoplasm (purple). Along the centre of the cell cytoplasm is the nuclear material (black lines).