Table of Contents
- 1 What color would it be if it was Gram stained correctly?
- 2 How would you define a properly prepared bacterial smear?
- 3 What is the hallmark of a good bacterial smear?
- 4 What color will a Gram-positive cell stain?
- 5 What is stained smear preparation?
- 6 How would you describe a properly prepared bacterial smear what does it look like not how is it prepared?
- 7 What should be the result of staining a bacterial smear with a mixture of Congo Red and methylene blue?
- 8 What happens if you over Decolorize in the Gram stain procedure?
- 9 How do you clean a smear after staining?
- 10 How does a properly prepared smear work?
- 11 Why is it important to avoid preparing a thick smear?
What color would it be if it was Gram stained correctly?
At the end of the gram staining procedure, gram positive cells will be stained a purplish-blue color. Gram negative cells also take up crystal violet, and the iodine forms a crystal violet-iodine complex in the cells as it did in the gram positive cells.
How would you define a properly prepared bacterial smear?
A properly prepared smear accomplishes two things. It causes bacteria to adhere to a slide so that they can be stained and observed. It also kills them, rendering pathogenic bacteria safe to handle. An objective in preparing smears is to learn to recognize the correct density of bacteria to place on the slide.
What should be the result of staining a bacterial smear?
What should be the result of staining a bacterial smear with a mixture of eosin and methylene blue? The smears background would turn out red while the cells would turn out blue. Predict the effect on Gram-positive & Gram-negative cells of the following “mistakes” made when performing a Gram stain.
What is the hallmark of a good bacterial smear?
What are the hallmarks of a well-made smear? A well-made smear is made up of a single layer of cells with open space between cells.
What color will a Gram-positive cell stain?
The Gram stain procedure distinguishes between Gram positive and Gram negative groups by coloring these cells red or violet. Gram positive bacteria stain violet due to the presence of a thick layer of peptidoglycan in their cell walls, which retains the crystal violet these cells are stained with.
Why is Gram-positive stain purple?
gram stain test Gram-positive bacteria remain purple because they have a single thick cell wall that is not easily penetrated by the solvent; gram-negative bacteria, however, are decolorized because they have cell walls with much thinner layers that allow removal of the dye by the solvent.
What is stained smear preparation?
The first step in most bacterial staining procedures is the preparation of a smear. In a smear preparation, cells from a culture are spread in a thin film over a small area of a microscope slide, dried, and then fixed to the slide by heating or other chemical fixatives.
How would you describe a properly prepared bacterial smear what does it look like not how is it prepared?
How would you define a properly prepared bacterial smear? A properly prepared bacterial smear would mean the bacteria are evenly spread out and properly fixed. This way they won’t wash off with DI water.
How do you interpret Gram stain results?
A Gram stain is colored purple. When the stain combines with bacteria in a sample, the bacteria will either stay purple or turn pink or red. If the bacteria stays purple, they are Gram-positive. If the bacteria turns pink or red, they are Gram-negative.
What should be the result of staining a bacterial smear with a mixture of Congo Red and methylene blue?
Eosin is a red stain and methylene blue is blue. What should be the result of staining a bacterial smear with a mixture of eosin and methylene blue? Methylene blue–is basic The smears background would turn out red while the cells would turn out blue.
What happens if you over Decolorize in the Gram stain procedure?
Over-decolorizing will lead to an erroneous result where gram-positive cells may stain pink to red indicating a gram-negative result, and under-decolorizing will lead to an erroneous result where gram-negative cells may appear blue to purple indicating a gram-positive result.
How do you make a Gram stain smear?
Below are some guidelines for preparing a smear for a Gram-stain.
- Place one needle of solid bacterial growth or two loops.
- If working from a solid medium, add one drop (and only one drop)
- Now, with your inoculating loop, mix the specimen with the water.
- Place the slide on a slide warmer and wait for it to dry.
How do you clean a smear after staining?
Place slide with heat fixed smear on staining tray. Gently flood smear with crystal violet and let stand for 1 minute. Tilt the slide slightly and gently rinse with tap water or distilled water using a wash bottle. Gently flood the smear with Gram’s iodine and let stand for 1 minute.
How does a properly prepared smear work?
A properly prepared smear accomplishes two things. It causes bacteria to adhere to a slide so that they can be stained and observed. It also kills them, rendering pathogenic bacteria safe to handle. An objective in preparing smears is to learn to recognize the correct density of bacteria to place on the slide.
How do I prepare a smear from a colony?
To prepare a smear from a colony, place a loopful (~25 µl) of deionized water over the circled area. Aseptically remove a barely visible amount of material from a culture with a loop or stick and use the loop or stick to mix it with the drop. Try to disperse the culture material completely, so that there are no visible chunks of material.
Why is it important to avoid preparing a thick smear?
Please note: It is very important to prevent preparing thick, dense smears which contain an excess of the bacterial sample. A very thick smear diminishes the amount of light that can pass through, thus making it difficult to visualize the morphology of single cells. Smears typically require only a small amount of bacterial culture.