Which type of bacteria is described as sphere-shaped?

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

Answer: (D)

The type of bacteria described as sphere-shaped is known as cocci. This term originates from the Greek word for "berry," reflecting the round shape of these microorganisms. Cocci can exist singularly or in arrangements, such as pairs (diplococci), chains (streptococci), or clusters (staphylococci). Their spherical structure allows them to have a different method of reproduction compared to rod-shaped bacteria (bacilli) or spiral-shaped bacteria (spirilla).

In contrast, bacilli are rod-shaped bacteria, which affects their motility and how they connect with each other. Spirilla are characterized by their spiral shape, which gives them a distinct appearance and influences their movement in a fluid environment. Understanding these shapes is crucial for microbiology, as it aids in identifying and categorizing bacteria. Therefore, recognizing that cocci are spherical is essential for anyone studying bacterial morphology and its implications in health and disease.