Cocci bacteria are bacteria that are spherical or oval in shape. The three basic shapes of bacteria are coccus, bacillus and spiral. Cocci bacteria can form arrangements that have different names.
Cocci bacteria that form pairs are called diplococci. Streptococci feature long chains of bacteria. Cocci bacteria that form clusters that look like grapes are called staphylococci, whereas those that form groups of four are called tetrads.
A single coccus bacteria can measure from 0.5 to 1 micrometer in diameter. Sometimes, cocci bacteria are not completely spherical. They can be oval or flattened on the sides, especially if they lie next to one another. These bacteria can also exist by themselves. Cocci bacteria do not have to be taxonomically related to one another.