Final answer:
Staphylococcus species form clusters and are catalase-positive, while Streptococcus species form chains and are catalase-negative; these characteristics are used to differentiate between the two genera.
Step-by-step explanation:
The arrangement of Staphylococcus and Streptococcus bacteria is a key characteristic that differentiates these two genera. Staphylococcus species typically appear in grape-like clusters. This is reflective of their name, which comes from the Greek for "bunches of grapes."
On the other hand, Streptococcus species are known for their arrangement in chains. The name Streptococcus is derived from the Greek word that means "twisted chain," and this is evident in their microscopic morphology which shows chains of cocci.
Both of these types of bacteria are gram-positive cocci. However, they can be easily distinguished not only by their physical arrangement but also by the catalase test.
Staphylococcus species are catalase-positive, which means they produce the enzyme catalase, while Streptococcus species are catalase-negative and do not produce this enzyme.