Staphylococcus sp. False-colour scanning electron micrograph (SEM) of a colony of the spherical genus of bacteria, Staphylococcus sp. These gram- positive bacteria appear in groups that resemble clusters of grapes (as here), but are also observed individually, in pairs or in short chains. They are significant human pathogens, causing diseases ranging from superficial skin infections to life-threatening systemic illness. Of the large number of species, three are commonly associated with human disease: S. aureus, S. epidermidis & S. saprophyticus. Magnification: x4500 at 6x7cm size.