Which of the following refers to spiral-shaped prokaryotes?

The term that refers to spiral-shaped prokaryotes is indeed "spirilla." Sprilla are characterized by their helical shape, which can range from simple curves to more tightly coiled forms. This morphology is significant in microbiology because the structure of a bacterial cell can influence its movement, interaction with its environment, and pathogenicity.

Bacilli refer to rod-shaped bacteria, while cocci are spherical bacteria. Vibrios are a specific category of curved bacteria that resemble a comma shape or a single, elongated spiral, but they are not as tightly coiled as spirilla. Understanding these different shapes and their classifications is key in microbiology for identifying and studying various types of bacteria.