Final answer:
Spiral-shaped bacteria are typically classified as spirochetes, which are gram-negative and can be motile due to flagella running lengthwise in their structure.
Step-by-step explanation:
Spiral-shaped bacteria are likely to be placed with spirochetes. Spirochetes are known for their distinctive spiral shape and are classified as gram-negative bacteria, although they have unique characteristics that make them distinct from other gram-negative bacteria. Their structure includes flagella that run lengthwise between the inner and outer membranes in the periplasmic space, contributing to their motility and spiral form. While spirochetes can be free-living anaerobes, some are also known to be pathogenic.