Flagella of a spiral bacterium. Coloured transmission electron micrograph (TEM) of part of a bacterium with flagella attached (light blue). This bacterium is Anaerobiospirillum thomasii, a species of anaerobic spiral bacteria found in the gastrointestinal tract of humans and some animals. The bacteria normally have bipolar tufts of flagella, which propel the unicellular organism by beating with a whip-like motion. Magnification: x24,000 when printed 10 centimetres wide.