Final answer:
The helical structure of a Spirillum is more rigid compared to the flexible spring-shaped form of a spirochete.
Step-by-step explanation:
The helical structure of a Spirillum is more rigid than the spring-shaped form of a spirochete. A spirochete is characterized by its long, thin, spiral-shaped body and uses an axial filament for propulsion, which is similar to a flagellum but runs inside the cell body, making it highly motile. When comparing bacterial shapes, a Spirillum is known for its rigid helical form, in contrast to the more flexible spirochetes. Spirochetes are characterized by their long, spiral-shaped bodies and are highly motile, using their axial filament to propel themselves. The axial filament is similar to a flagellum, but it wraps around the cell and runs inside the cell body of a spirochete. Vibrios, on the other hand, have a characteristic curved rod shape.