The genus name Streptococcus refers to grouping cells of particular shape. Streptococci are Gram-positive bacteria that form chains of spherical cells. The word "strepto-" comes from the Greek word for "chain," and "coccus" comes from the Greek word for "berry." Streptococci are commonly found in the throats and intestines of humans and animals, and they can cause a variety of infections, including strep throat, scarlet fever, and pneumonia.