Ch. 3 - Introduction to Prokaryotic Cells

Norman-McKay- Microbiology: Basic and Clinical Principles 2nd Edition

Norman-McKay2nd EditionMicrobiology: Basic and Clinical PrinciplesISBN: 9780137661619Not the one you use?Change textbook

Norman-McKay 2nd Edition

Ch. 3 - Introduction to Prokaryotic Cells

Problem 10

Chapter 3, Problem 10

Complete the Venn diagram that compares and contrasts Gram-positive and Gram-negative bacteria.

Verified step by step guidance

Step 1: Identify the key characteristics unique to Gram-positive bacteria, such as a thick peptidoglycan layer in their cell wall, presence of teichoic acids, and retention of the crystal violet stain during Gram staining.

Step 2: Identify the key characteristics unique to Gram-negative bacteria, including a thin peptidoglycan layer, an outer membrane containing lipopolysaccharides (LPS), and the inability to retain the crystal violet stain, instead taking up the counterstain (safranin) and appearing pink/red.

Step 3: Determine the shared characteristics between Gram-positive and Gram-negative bacteria, such as having a cell membrane, ribosomes, DNA, and the ability to reproduce by binary fission.

Step 4: Place the unique features of Gram-positive bacteria in one circle of the Venn diagram, the unique features of Gram-negative bacteria in the other circle, and the shared features in the overlapping section.

Step 5: Review the completed Venn diagram to ensure all relevant structural and staining differences, as well as common bacterial traits, are accurately represented.

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Key Concepts

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

Cell Wall Structure

Gram-positive bacteria have a thick peptidoglycan layer in their cell walls, which retains the crystal violet stain, appearing purple under a microscope. In contrast, Gram-negative bacteria have a thin peptidoglycan layer and an outer membrane containing lipopolysaccharides, causing them to appear pink after Gram staining.

Gram Staining Technique

Gram staining differentiates bacteria based on their cell wall properties. The process involves staining with crystal violet, iodine treatment, alcohol decolorization, and counterstaining with safranin. Gram-positive bacteria retain the violet dye, while Gram-negative bacteria lose it and take up the pink counterstain.

Physiological and Pathogenic Differences

Gram-negative bacteria often have higher resistance to antibiotics due to their outer membrane, which acts as a barrier. They also tend to produce endotoxins from lipopolysaccharides. Gram-positive bacteria lack this outer membrane but may produce exotoxins and have different susceptibility to antibiotics.

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Related Practice

Textbook Question

Which of the following would you expect to find in acid-fast cell walls? Select all that

apply.

a. Peptidoglycan

b. Phospholipids

c. Lipopolysaccharide

d. Lipid A

e. Mycolic acid

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Textbook Question

Describe what would occur if a cell with a damaged cell wall was placed in each of the following environments:

Isotonic environment
Hypertonic environment
Hypotonic environment

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Textbook Question

Certain bacteria can form endospores in order to __________________.

a. Reproduce

b. Survive harsh conditions

c. Cause recurrent infections

d. Adhere to host tissues

e. Avoid the immune system of a host

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Textbook Question

Complete the table by answering yes or no for each question.

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Textbook Question

Match the cellular structures to their functions. Many statements will be used more than once; some structures may be matched to more than one functional description.

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Textbook Question

State the shape and arrangement of the pictured bacterial samples. <IMAGE>

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