PRE-LAB: STAINING & LAB 11 Staining - Gram Staining

You are Gram staining a known sample that contains both gram-positive and gram-negative bacteria. After complete the staining, you realize that you performed the decolorizer step for 10 minutes instead of 10 seconds! You are Gram staining a known sample that contains bothgram-positive and gram-negative bacteria. After you complete the staining, you realize that you did not use the alcohol bottle at all.

A. Gram-positive organisms might incorrectly stain red. Gram-negative Gram-positive

Why might it be important to perform a Gram stain on bacterial cells?

As part of the information used to choose an appropriate antibiotic treatment

Endospores are difficult to stain due to which of the following?

Endospores have a thick spore coat. Endospores exclude dye.

Omitting the steaming in an endospore stain would result in which of the following?

Endospores would not take up stain.

Which of the following clinically important organisms are considered acid-fast?

Mycobacterium leprae Mycobacterium tuberculosis

Which of the following is a nonpathogen that is safely used in teaching labs?

Mycobacterium smegmatis

Which of the following is a significant lipid component of the cell walls of acid-fast bacteria?

Mycolic acid

What is stained by the counterstain in the acid-fast stain procedure?

The non-acid-fast organisms on the slide

Which of the following are functions of the bacterial capsule?

Protection Adherence

Which of the following apply to endospores?

They are used for surviving adverse environmental conditions.

Which is not a disease caused by an endospore forming organism?

Tuberculosis

What reagent is used to stain the vegetative cells in the endospore staining procedure?

Safranin

Which three of the following terms all refer to a similar structure?

Slime layer Glycocalyx Capsule

Which occurs first in the endospore stain?

Staining of the endospore

Which of the following are diseases caused by an acid-fast bacterium?

TB (tuberculosis) Leprosy

Which of the following structures makes it difficult to stain endospores?

The endospore coat.

In the acid-fast staining method, the highly concentrated stain ( ) is used to penetrate the cell wall and colorize acid-fast bacterial cells.

carbolfuchsin

In a differential staining technique, a _____ is used to remove the primary stain from the bacterial cell.

decolorizer

The type of stain designed to show differences between various organisms or cellular structures is referred to as a (n) stain, whereas a (n) stain uses only one dye to stain all cell types.

differential simple

In order to withstand hostile conditions and facilitate survival, some bacteria produce resistant structures known as ( ) .

endospores

In order to withstand hostile conditions and facilitate survival, some bacteria produce resistant structures known as .

endospores

is used to stain the endospore in the endospore staining procedure.

malachite green

The counterstain used in the acid-fast stain is

methylene blue.

A chemical that fixes dye in or on cells by forming an insoluble compound is referred to as a (n)

mordant.

A chemical that fixes dye in or on cells by forming an insoluble compound is referred to as a(n)

mordant.

Gram- ( ) cell walls contain a thin layer of peptidoglycan, whereas Gram- ( ) cell walls contain a thick layer of peptidoglycan.

negative positive

The first dye applied in a differential staining technique is referred to as the ( ) stain.

primary

After correct Gram staining, the gram-negative cells will appear , ( ) whereas the gram-positive cells appear ( ) .

red; purple

The name of the counterstain, or secondary stain, typically used in the Gram-stain technique is ( ).

safranin

Encapsulated organisms are difficult to directly stain because

the capsule does not react with most stains. the capsule is not permeable to stains.

A(n) _____ is a metabolically active and growing cell.

vegetative cell

What does negative staining help to increase?

Contrast

Place the steps of the endospore stain in the correct sequence.

1. Apply malachite green to smear 2. Cover smear with piece of paper towel. 3. Rinse 4. Apply safranin to smear. 5. Rinse and blot dry. 6. Stem over water bath.

Place these reagents in the proper order of their use in the Gram-staining technique.

1. Crystal Violet 2. Gram's iodine 3. Decolorizer 4. Safranin

Place the following steps of the acid-fast stain in the proper sequence.

1. Stain with carbolfuchsin 2. Rinse off excess primary stain. 3. Decolorize with acid alcohol. 4. Rinse with water to stop the decolorization process. 5. Counterstain with methylene blue. 6. Rinse off excess counterstain 7. Blot Dry.

Based on what you understood from the video, which of the following statements are correct?

A. This image likely depicts a Gram-stained bacterial smear. D. This image shows cell arrangement of streptococci. F. This image shows a cell morphology of cocci.

Which of the following is not a common staining method used for visualization of bacteria?

All of the staining methods above are commonly used.

Your Gram stain is complete and correct. Which of the following statements would apply to the image you see?Select all that apply

B. You can observe gram-negative bacilli on this field. C. You can observe gram-positive cocci on this field.

Which of the following bacterial genera are capable of producing endospores?

Bacillus Clostridium

In a negative stain, which of the following is stained?

Background

The acid-fast cell wall contains large amounts of mycolic acid. Which of the following can be attributed to the presence of mycolic acid?

Chemicals cannot readily penetrate the cell wall of these cells. Mycolic acid makes the cells more difficult to stain.

Which of the following is not a differential stain? Multiple choice question.

Capsule stain

What is the initial stain used in the acid-fast stain?

Carbolfuchsin

You are Gram staining a known sample that contains both gram-positive and gram-negative bacteria. After you complete the staining, you observe the following. Which of the following statements would apply to the image you see? You Gram staining a known ample that contains both gram-positive and gram-negative bacteria. After complete the staining, you realize that you did not perform the safranin step.

D. This image could be explained by omission of the Gram's iodine step, causing all cells to appear gram-negative. C. Gram-negative organisms might not be visible.

Capsules are easily stained using basic staining techniques.

False

Which of the following correctly describe how the Gram stain works to color different types of cells?

Gram-negative cells are decolorized by alcohol and stained by the pink/red secondary stain. Gram-positive cells retain the purple dye-mordant complex because of their thick layer of peptidoglycan.

What might happen if you omitted the safranin step while performing the Gram stain on a mixed culture of gram-positive and gram-negative cells?

Gram-negative organisms might not be easily visible.

What type of cell wall contains a thick layer of peptidoglycan and no outer membrane?

Gram-positive

The _____ stain provides critical information about the peptidoglycan structure of the cell wall.

Gram

Match the staining procedure with its description.

Gram Stain: A stain that can differentiate between cells that have thick or thin layers of peptidoglycan in their cell walls. Acid-fast Stain: A stain that would be appropriate for cells that contain mycolic acid in their cell walls. Capsule Stain: A stain that enables you to effectively visualize a bacterium's capsule.

What is used as the mordant in the Gram-staining technique?

Gram's iodine

What type of bacterial cell wall is composed of a thin layer of peptidoglycan and an outer membrane?

Gram-negative

If you forget to use the decolorizer, which cell type(s) will appear purple?

Gram-negative Gram-positive

If safranin was omitted from the endospore stain, what color would the endospores appear?

Green

In order to ensure that dye penetrates the spore coat and stains the endospore, which of the following is needed?

Heat

Which of the following describes the correct sequence of the Gram-stain procedure?

Heat-fixed slide; use of crystal violet, iodine, decolorizer, and safranin.

Why is steam used in the endospore staining procedure?

It helps drive the green stain into the stain-resistant endospore.

Which is not used in the endospore staining procedure?

Methylene blue Crystal Violet

What is the purpose of the Gram staining technique?

To characterize unknown bacteriac

What is the purpose of a negative stain?

To visualize a capsule (if present) To visualize the bacteria

A capsule can protect a cell from attack by the immune system.

True