 The type IV secretion system is divided into type IVA and type IVB based on genetic ancestry.Notable instances of the type IV secretion system include the plasmid insertion into plants of "Agrobacterium tumefaciens", the toxin delivery methods of "Bordetella pertussis" (whooping cough) and "Legionella pneumophila" (Legionnaires' disease), and the F sex pilus.The type IV secretion system is a protein complex found in prokaryotes used to transport DNA, proteins, or effector molecules from the cytoplasm to the extracellular space beyond the cell.