Pseudomonas aeruginosa. Coloured scanning electron micrograph (SEM) of Pseudomonas aeruginosa bacteria. They are Gram-negative, rod-shaped bacteria, with flagellae (one seen as a hair-like strand at left) for movement. This species of Pseudomonas is common in the human intestine, but can cause serious wound, skin and urinary tract infections. It can also multiply in the warm, moist conditions prevailing inside baby incubators or ventilating machines and so be inhaled in large numbers. Such infections of the respiratory tract are usually harmless, but sometimes result in dangerous pneumonia. Magnification: x15,000 at 6x4.5cm size.