Simple Stains Mastering Microbiology Lab Homework

Other than morphology, what else could you learn from the use of a simple stain? Size of the organism Can indicate the presence of a contaminating organism A simple stain can help you discern the size of the organism, the quality of the smear preparation, and can also help indicate whether or not contaminating organisms are present. Quality of smear preparation technique

A simple stain can help you discern the size of the organism, the quality of the smear preparation, and can also help indicate whether or not contaminating organisms are present.

What is the purpose of allowing the bacterial smear to dry once it has been placed onto the surface of the slide? Drying helps remove excess water to ensure optimal heat fixation. Air-drying adheres the bacteria to the slide. Air-drying ensures that the smear is thin enough to stain. The air-drying step coagulates the proteins in the bacteria.

Drying helps remove excess water to ensure optimal heat fixation.

What is the purpose of heat fixation? Heat fixation ensures the elimination of contaminating organisms from the smear preparation. Heat fixation adheres the cells to the slide and coagulates the bacterial proteins, effectively killing the bacteria. Heat fixation is necessary to provide contrast between the cells and the background. Heat-fixation ensures that the smear is thin enough for good visualization of individual cells.

Heat fixation adheres the cells to the slide and coagulates the bacterial proteins, effectively killing the bacteria

Why does the presence of grease or dirt on a glass slide result in a poor smear preparation? The grease and dirt can interfere with heat fixation. The grease and dirt can contaminate the inoculating instrument. The grease and dirt can create artifacts that interfere with accurate visualization of the organisms. The grease and dirt will neutralize the charges of the cell wall components and the stain will not be attracted to the cells.

The grease and dirt can create artifacts that interfere with accurate visualization of the organisms.

What is a correct association regarding the difference between an acidic dye and a basic dye? Acidic = Negatively charged chromogen; Basic = Positively charged chromogen Acidic = Positively charged chromogen; Basic = Negatively charged chromogen Acidic = Binds to negatively charged cell components; Basic = Repelled from negatively charged cell components Acidic = Binds to negatively charged cell components; Basic = Binds to positively charged cell components

Acidic = Negatively charged chromogen; Basic = Positively charged chromogen

It is necessary to dilute the bacterial inoculum when transferring from what type of culture media? Agar slants Any solid (agar-based) media Broth culture Agar plates

Any solid (agar-based) media

Which of the following describes streptobacilli? Clusters of spherically shaped cells Chains of rod-shaped cells Clusters of rod-shaped cells Chains of spherically shaped cells

Chains of rod-shaped cells

Which of the following describes streptococci? Chains of spherically shaped cells Chains of rod-shaped cells Clusters of rod-shaped cells Clusters of spherically shaped cells

Chains of spherically shaped cells

Which of the following describes staphylococci? Chains of rod-shaped cells Chains of spherically shaped cells Clusters of rod-shaped cells Clusters of spherically shaped cells

Clusters of spherically shaped cells

Why is it important not to use thick or dense bacterial smears? The stain may not be able to penetrate a thick smear. The cells will be too concentrated, making it difficult to visualize individual cells and to determine cellular morphology. This type of preparation diminishes the amount of light that can pass through the slide. In a thick smear the bacteria will be too concentrated, reducing the amount of light passing through the slide, the stain may not penetrate adequately, and it will be difficult to visualize individual cells.

In a thick smear the bacteria will be too concentrated, reducing the amount of light passing through the slide, the stain may not penetrate adequately, and it will be difficult to visualize individual cells.

During heat fixation, it is important that the slide be passed only 2-3 times through the outer portion of the Bunsen burner flame to prevent overheating. Overheating can cause which of the following to occur? Expansion of the cells, causing them to burst Melting of the glass slide Plasmolysis of the bacterial cell wall, distorting the cell morphology Loss of the specimen from the surface of the slide

Plasmolysis of the bacterial cell wall, distorting the cell morphology

What would you expect to happen if you failed to heat fix the slide? The bacteria will not arrange in clusters The bacteria are likely to get washed away during the staining procedure The bacteria will not be attracted to the chromogen of the basic stain All of the above

The bacteria are likely to get washed away during the staining procedure

Why is it necessary to stain microorganisms with biological stains in order to visualize them with a microscope? The stain adheres the bacteria to the slide. The stain provides necessary contrast between the cells and the background. The stain magnifies the bacteria. The stain kills the bacteria.

The stain provides necessary contrast between the cells and the background.

What is the purpose of holding the slide parallel to the stream of water during the final rinsing step? To avoid splashing water onto your hands To avoid dislodging the organisms from the surface of the slide To increase the force of the running water in order to properly rinse the excess stain from the slide None of the above

To avoid dislodging the organisms from the surface of the slide