Staphylococcus aureus (G+ cocci) and K.pneumoniae (G- rods) micrograph
Staphylococcus under the microscope, Gram-stain (smear made from colonies cultivated on tryptic soy agar)
Members of the genus Staphylococcus are round , Gram-positive cocci that can divide in any plane and tend to be arranged in grapelike clusters (from Greek staphyle, bunch of grapes). In stained preparations Staphylococcus aureus appears as irregular groups of cocci, single elements, pairs and tetrads (short chains may also be seen).
The individual cocci are quite uniform in size, 0.8 to 1.0 µm in diameter and neither flagellae nor spores are present. The cocci are spherical, but their opposing surfaces may appear to be somewhat flattened.