False-colour scanning electron micrograph (SEM) of a colony of Legionella pneumophila, the bacteria causing Legionnaire's disease, a severe & often fatal form of lobar pneumonia. The weakly-staining Gram-negative bacterium is elongated with a single flagellum for motility. The disease obtained its name after an outbreak at an American Legion convention in Pennsylvania in 1976. L. pneumophila is known to be distributed in water; water-tanks, shower heads, and cooling tanks for air- conditioning systems in large buildings are favoured environments. Infection is likely to occur through inhalation of the bacteria in water droplets. Mag: x1,000 35mm, x2,000 at 6x7cm size.