In a diagram showing different bacterial shapes, which drawing would possess an axial filament?

• A. A coccus
• B. A bacillus
• C. A vibrio
• D. A spirochete

Answer: (D)

Verified step by step guidance

1. Step 1: Understand what an axial filament is. An axial filament is a specialized structure found in certain bacteria, specifically spirochetes, that allows them to move in a corkscrew motion. It is essentially a type of flagella located between the cell wall and outer membrane, wrapped around the cell body.
2. Step 2: Review the common bacterial shapes: cocci (spherical), bacilli (rod-shaped), vibrio (comma-shaped), and spirochetes (spiral-shaped). Each shape has distinct structural features.
3. Step 3: Recognize that axial filaments are unique to spirochetes. Unlike other bacteria that have external flagella, spirochetes have internal flagella called axial filaments that run along the length of the cell between the outer membrane and the cell wall.
4. Step 4: Analyze the diagram by identifying the shape of each bacterium. The drawing that shows a spiral-shaped bacterium with internal flagella wrapped around the cell body corresponds to a spirochete and thus possesses an axial filament.
5. Step 5: Conclude that among the options (coccus, bacillus, vibrio, spirochete), only the spirochete has an axial filament, which is responsible for its distinctive motility.