Helicobacter pylori. Coloured transmission electron micrograph of the bacterium Helicobacter pylori (formerly called Campylobacter pyloridis). It is a curved, or spiral, Gram- negative bacilli with flagellae at one end (seen here) that make it highly motile. Helicobacter pylori is linked with the formation of stomach ulcers, through observation of the bacterium in biopsy specimens from patients with active chronic gastritis & peptic ulcers. Magnification: x9,000 at 6x7cm size.