Spiral: Also known as spirilla, these bacteria are shaped like spirals or helixes. If their coil is very tight, they are known as spirochetes. Examples include Treponema pallidum, which causes syphilis.
Spherical: Also known as cocci, these bacteria are shaped like balls. Examples include Staphylococcus aureus, which forms grape-like clusters, and Streptococcus, which is responsible for strep throat.