The bacterial cell wall is a rigid structure that provides structural support and helps maintain the shape of the bacterial cell. It is responsible for giving bacteria their characteristic shapes, such as rod-shaped (bacilli), spherical (cocci), or spiral (spirilla), and it also plays a role in protecting the cell from osmotic pressure changes.

The capsule (option B) and slime (Option D) are not primarily responsible for maintaining the cell shape but may have other functions, such as protecting the cell or aiding in adhesion. Option C mentions both the cell wall and slime, but the cell wall is the primary component responsible for shape maintenance.