Which arrangement describes spiral-shaped bacteria?

• A. Spirilla
• B. Cocci
• C. Bacilli
• D. Vibrios

Answer: (A)

Recognizing bacterial shapes helps you classify them quickly. Spiral-shaped bacteria are described as spirilla. They twist in a helical form, often appearing as rigid spirals with external flagella that propel them. The other options correspond to different shapes: cocci are spherical, bacilli are rod-shaped, and vibrios are curved, comma-shaped rods. While there are also spirochetes, another spiral type that is more flexible, the term spirilla specifically refers to the rigid spiral shape, making it the correct label for spiral-shaped bacteria in this context.