Gram-Positive Bacteria Quiz

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Questions and Answers

What is the defining characteristic of gram-positive bacteria in the Gram stain test?

They retain the safranin counterstain
They retain the crystal violet stain (correct)
They have a thin peptidoglycan layer
They have an outer membrane that degrades during the test

What happens to the crystal violet stain in gram-negative bacteria during the Gram stain test?

It becomes more visible under the optical microscope
It is washed away during the decolorization stage (correct)
It is retained due to a thick peptidoglycan layer
It turns into a different color due to the bacterial outer membrane

What is the role of peptidoglycan in the Gram stain test?

It degrades the outer membrane of gram-negative bacteria
It reacts with the safranin counterstain
It changes color during the decolorization stage
It retains the crystal violet stain in gram-positive bacteria (correct)

What effect does alcohol have on gram-negative bacteria during the Gram stain test?

<p>It degrades the outer membrane, making the cell wall more porous (A)</p> Signup and view all the answers

Why do gram-negative bacteria take up the safranin counterstain in the Gram stain test?

<p>Their peptidoglycan layer is much thinner (B)</p> Signup and view all the answers

Flashcards

What's special about gram-positive bacteria?

Gram-positive bacteria retain the crystal violet stain during the Gram stain test.

What happens to the stain in gram-negative bacteria?

The crystal violet stain is washed away from gram-negative bacteria during the decolorization stage.

What's the role of peptidoglycan?

Peptidoglycan holds onto the crystal violet stain in gram-positive bacteria, preventing it from being washed away.

How does alcohol impact gram-negative bacteria?

Alcohol weakens the outer membrane of gram-negative bacteria, making their cell walls more porous and allowing the dye to wash away.

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Why do gram-negative bacteria pick up safranin?

Gram-negative bacteria have a thinner peptidoglycan layer, making them susceptible to losing the crystal violet stain. They take up the counterstain, safranin, to become visible.

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Study Notes

Gram Stain Test Characteristics

The defining characteristic of gram-positive bacteria in the Gram stain test is the retention of crystal violet stain, which turns them purple.
In gram-negative bacteria, the crystal violet stain is decolorized, meaning it is removed, during the Gram stain test.

Peptidoglycan and its Role

Peptidoglycan, a thick multilayered peptidoglycan wall, is present in gram-positive bacteria, allowing them to retain the crystal violet stain.

Effects of Alcohol and Safranin Counterstain

Alcohol decolorizes gram-negative bacteria, allowing the safranin counterstain to take its place and turn them pink.
Gram-negative bacteria take up the safranin counterstain because they have been decolorized by the alcohol and do not retain the crystal violet stain.

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Description

Test your knowledge of bacteriology with this quiz on gram-positive bacteria. Explore their unique characteristics, cell wall structure, and classification based on the Gram stain test. See how much you know about these vital microorganisms.