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Ch. 11 - Characterizing and Classifying Prokaryotes
Bauman - Microbiology with Diseases by Taxonomy 6th Edition
Bauman6th EditionMicrobiology with Diseases by TaxonomyISBN: 9780134832302Not the one you use?Change textbook
Chapter 11, Problem 3

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
Step 1: Understand the shape terminology for prokaryotic cells. 'Cocci' refers to spherical-shaped bacteria, 'Bacilli' refers to rod-shaped bacteria, 'Spirilla' refers to rigid spiral-shaped bacteria, and 'Spirochetes' refers to flexible spiral-shaped bacteria.
Step 2: Identify the key descriptor in the question: 'stiff, spiral-shaped prokaryotic cells.' This indicates the cells have a spiral shape and are rigid rather than flexible.
Step 3: Compare the options with the description: Cocci (spherical) and Bacilli (rod-shaped) do not match the spiral shape, so they can be excluded.
Step 4: Between 'Spirilla' and 'Spirochetes,' note that Spirilla are known to be rigid or stiff spiral-shaped bacteria, while Spirochetes are more flexible and have a unique corkscrew motion.
Step 5: Conclude that the term best describing stiff, spiral-shaped prokaryotic cells is 'Spirilla.'

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Prokaryotic Cell Shapes

Prokaryotic cells have distinct shapes that help in their identification. Common shapes include cocci (spherical), bacilli (rod-shaped), and spiral forms. Understanding these shapes is fundamental to classifying bacteria and predicting their behavior.
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Spiral-Shaped Bacteria Types

Spiral-shaped bacteria are categorized mainly into spirilla and spirochetes. Spirilla are rigid, spiral-shaped bacteria with external flagella, while spirochetes are flexible and have internal flagella, allowing different modes of movement.
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Terminology for Bacterial Morphology

Accurate terminology is essential in microbiology to describe bacterial morphology. Terms like cocci, bacilli, spirilla, and spirochetes specify shape and structural features, aiding in identification and understanding of bacterial physiology.
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