Which of the following terms best describes stiff, spiral-shaped prokaryotic cells?


a. cocci
b. bacilli
c. spirilla
d. spirochetes

Verified step by step guidance

1. Identify the key characteristics of each term provided in the options.
2. Cocci are spherical-shaped prokaryotic cells, so eliminate option a.
3. Bacilli are rod-shaped prokaryotic cells, so eliminate option b.
4. Spirilla are stiff, spiral-shaped prokaryotic cells, which matches the description given in the problem.
5. Spirochetes are flexible, spiral-shaped prokaryotic cells, so eliminate option d.

Key Concepts

Prokaryotic Cell Structure

Prokaryotic cells are unicellular organisms that lack a nucleus and membrane-bound organelles. They are characterized by their simple structure, which includes a cell membrane, cytoplasm, and genetic material in the form of a single circular DNA molecule. Understanding the basic structure of prokaryotic cells is essential for identifying their various shapes and classifications.

Bacterial Morphology

Bacterial morphology refers to the study of the shape and arrangement of bacteria. Common shapes include cocci (spherical), bacilli (rod-shaped), spirilla (spiral-shaped with rigid bodies), and spirochetes (flexible spiral-shaped). Recognizing these shapes is crucial for microbiologists in classifying and identifying bacterial species.

Spirilla vs. Spirochetes

Spirilla and spirochetes are both types of spiral-shaped bacteria, but they differ in structure and flexibility. Spirilla are rigid and have a helical shape, while spirochetes are more flexible and can move in a corkscrew motion. This distinction is important for understanding their behavior, ecology, and the diseases they may cause.