Basic bacterial morphology: the common term for straight, rod-shaped bacteria is which of the following?

Introduction / Context:
Bacterial morphology is a first-pass identification tool. Recognizing the correct terms for basic shapes helps interpret Gram stains and culture results quickly during clinical or environmental microbiology workups.

Given Data / Assumptions:

• Straight, rod-shaped cells are being described.
• We compare names for spheres, rods, helical forms, and variable shapes.

Concept / Approach:
“Bacilli” (singular: bacillus) are straight rods. “Cocci” are spheres; “spirilla/spirochetes” are helical or spiral forms. “Pleomorphic” describes variability in shape rather than a single geometric category.

Step-by-Step Solution:

Verification / Alternative check:
Textbook diagrams and Gram-stain atlases consistently label straight rods as bacilli.

Why Other Options Are Wrong:

• Cooci (misspelling of cocci): spherical, not rods.
• Spirilla: spiral/helical forms.
• Pleomorphic: variable forms, not specifically straight rods.

Common Pitfalls:
Confusing “Bacillus” (a genus) with “bacilli” (rod shape in general); context clarifies usage.

Final Answer:
bacilli