Bacterial morphology terminology: What is the common term for bacteria that are spherical in shape?

Introduction / Context:
Basic bacterial morphology is a foundation for laboratory identification, gram staining interpretation, and understanding colony and cell arrangements. Three primary shapes are commonly introduced: cocci (spherical), bacilli (rod-shaped), and spirilla/spirochetes (spiral forms).

Given Data / Assumptions:

• The question asks for the term that denotes spherical bacteria.
• Common shape terms are standard across textbooks and lab manuals.
• No special staining or arrangement qualifiers are required to answer.

Concept / Approach:

“Cocci” refers to spherical or nearly spherical bacterial cells. Typical examples include Staphylococcus (grape-like clusters) and Streptococcus (chains). Shape complements staining and arrangement to aid in preliminary identification before biochemical or molecular tests confirm species.

Step-by-Step Solution:

Verification / Alternative check:

Observation under light microscopy with appropriate staining (e.g., Gram stain) readily distinguishes spherical cocci from rods and spirals. Clinical algorithms use this as an early branching point.

Why Other Options Are Wrong:

Bacilli are rods, not spheres.

Spirilla are spiral, corkscrew, or curved shapes.

Pleomorphic denotes variable morphology and does not specifically mean spherical.

Common Pitfalls:

Assuming arrangement (pairs, tetrads, clusters, chains) changes the basic shape term. Arrangement terms are additional descriptors layered on the fundamental shape category.

Final Answer:

Cocci