Staphylococcus bacteria. Coloured scanning electr- on micrograph (SEM) of Staphylococcus aureus bacteria (yellow) on human nasal epithelial cells. These gram-positive cocci (spherical bacteria) are adhering to mucus (blue) on the hair-like cilia which protrude from the epithelial cells. S. aureus is very common in humans, living harmlessly on the skin and in the nose, throat and large intestine. However it can multiply inside blocked skin pores, causing pus to build up and forming an acne spot or boil. Inside the body this bacteria may cause abscesses and suppurative infection. Magnification: x7, 000 at 6x6cm size. x24,900 at 8x8"~SQUARE"