Coloured scanning electron micrograph (SEM) of Pseudomonas aeruginosa, Gram-negative, aerobic, enteric, rod prokaryote (dividing). This bacterium produces a blue, Green pigment, pyocyanin, which characterizes the bluish pus produced by the infection. It is found in soil, water, skin flora, and most man-made environments throughout the world. Magnification: x2, 400 when shortest axis printed at 25 millimetres.