Helicobacter pylori bacterium, coloured transmission electron micrograph (TEM). This section through the bacterium shows a spherical body and several flagella (upper right, used for movement). This spherical or coccal form is not an active form, but is a dormant form adopted to survive adverse conditions. H. pylori (formerly named Campylobacter pyloridis or pylori) is a bacterium that infects the mucosal stomach lining. Some people go on to develop stomach ulcers due to the infection. Long-term infection is thought to increase risks of stomach cancer. Magnification: x43,500 when printed 10cm wide.