Which bacterial feature is a gelatinous coating that protects against phagocytosis and assists adhesion to surfaces?

• A. Capsule
• B. Plasmids
• C. Pili
• D. Endospore

Answer: (A)

The capsule is a gelatinous coating outside the cell wall that protects against phagocytosis and helps bacteria adhere to surfaces. This slimy layer, often made of polysaccharides (and sometimes proteins), acts as a shield that can mask bacterial surface structures from immune cells and reduce recognition, making it harder for macrophages to engulf the bacterium. At the same time, the capsule increases stickiness to host tissues and abiotic surfaces, promoting attachment and biofilm formation, which aids colonization and persistence in the environment. Plasmids are circular DNA elements that carry genes but don’t form a protective coating. Pili are hairlike appendages used for attachment and genetic exchange, not a general protective gelatinous layer. Endospores are dormant, highly resistant survival forms, not coatings. Thus, the capsule best fits the description.