False-colour transmission electron micrograph (TEM) of a group of the bacteria Helicobacter pylori (formerly called Campylobacter pylori). H. pylori is a curved, or spiral, Gram-negative bacillus with flagella at one end (not visible in this section) that make it highly motile. Helicobacter pylori has recently been linked with the formation of stomach ulcers, through observation of the bacterium in biopsy specimens from patients with active chronic gastritis & peptic ulcers. Magnification: x10,000 at 35mm size, x20,000 at 6x7cm size.