What term is used for chains of spherical bacteria?

The term used for chains of spherical bacteria is "streptococci." This term specifically refers to a genus of bacteria that are characterized by their arrangement in chains or pairs, resulting from their mode of cell division. Streptococci are Gram-positive cocci that can be responsible for a variety of infections, including strep throat, bacterial pneumonia, and skin infections.

The arrangement occurs due to the division of the cells in one plane, which leads to the formation of characteristic chains. This is in contrast to staphylococci, which are another group of bacteria that arrange themselves in clusters or “grape-like” formations due to their division in multiple planes.

Bacilli, on the other hand, refer to rod-shaped bacteria, and vibrios describe comma-shaped bacteria. Hence, these options do not pertain to the specific morphology of spherical bacteria forming chains.