Which one of the following is a specific structure of bacterial cell?

Explanation

The capsule is an outer wrapping or envelope found in certain bacterial cells but missing in others. The bacteria having it are called encapsulated and make smooth surfaced colonies. They are more virulent for the host and resistant against the host immune system. The bacteria which lack capsule are called non-encapsulated and make rough-surfaced colonies and are vulnerable to host immune system that is why they are genus less virulent.