||Caption: Prokaryote and eukaryote cell types - bacterium (prokaryote - Moraxella catarrhalis); protozoan (eukaryote - Trypanosoma sp.); human red blood cell (eukaryote). The bacterium, Moraxella catarrhalis, is a prokaryotic, gram-negative, aerobic, diplococcus bacterium (formerly known as Branhamella catarrhalis). It may colonize and cause respiratory tract infections in humans. M. catarrhalis has been implicated in a variety of infections, including: bronchitis, sinusitis, laryngitis, bronchopneumonia and otitis media. M. osloensis is another species that is pathogenic in humans. The trypanosome trypomastigote, Trypanosoma sp., is a eukaryotic, parasitic, hemoflagellated protozoan that causes trypanosomiasis (African sleeping sickness, Chagas disease). This trypanosome is a vector borne parasite transmitted by tsetse flies (Glossina spp.). The ribbon like flagellated trypomastigote is carried in the insects saliva (and feces) and enters the human host through a wound made by the fly. This protozoan infects the blood, lymph and spinal fluid and rapidly divides. Upon entering the cerebral spinal fluid the parasite can damage brain tissue causing eventually causing death. The human red blood cell (eukaryotic) is the most abundant type of cell in human blood, accounting for 40% of the blood volume. Each cubic millimeter of blood contains around five million of these tiny, flexible disc-shaped cells. The red color comes from the iron-containing protein hemoglobin, which picks up oxygen in the lungs and distributes it around the body. Because the cells have no nucleus and are subjected to constant physical action, they last only four months before being destroyed and broken down.