Aquaspirillum magnetotacticum, TEM

Coloured transmission electron micrograph (TEM) of Aquaspirillum magnetotacticum (also known as Magnetospirillum magnetotaticum), spirillum shaped bacterium. Spirilla are Gram-negative, aerobic heterotrophic bacteria with a helical or spiral shape. Their metabolism is respiratory and never fermentative. Unlike spirochetes, they have a rigid cell wall and are motile by means of ordinary polar flagella. Spirilla are inhabitants of microaerophilic aquatic environments. Most spirilla require or prefer that oxygen in their environment be present in an amount that is well below atmospheric concentration. Aquaspirillum are inhabitants of fresh water. They frequently contain magnetosomes (iron oxide granules) and exhibit the property of magnetotaxis (movement in relationship to the magnetic field of the earth). Magnification: x13,535 when shortest axis printed at 25 millimetres.