Table of Contents
- 1 Why is it important to heat fix a bacterial smear before staining?
- 2 What is the purpose of fixing the smear by heat?
- 3 What is the purpose of using heat to completely dry a smear after applying bacteria to a slide?
- 4 What is the purpose of applying a stain to a bacterial smear?
- 5 What is the purpose of preparing a bacterial smear?
- 6 What is bacterial smear?
- 7 Why do you have to heat fix a bacterial smear before?
- 8 Why is it important to fix the smear?
Why is it important to heat fix a bacterial smear before staining?
Bacterial smears are “heat fixed” on the microscope slide before staining to affix the cells to the slide so that they do not wash off during the staining procedure.
What is the purpose of fixing the smear by heat?
Heat fixing kills the bacteria in the smear, firmly adheres the smear to the slide, and allows the sample to more readily take up stains.
Why do we fix the smear before staining?
The preparation of a smear is required for many laboratory procedures, including the Gram-stain. The purpose of making a smear is to fix the bacteria onto the slide and to prevent the sample from being lost during a staining procedure.
Why does the bacterial smear needs to be heated when performing acid fast staining and spore staining?
The heat “melts” the waxy cell wall and permits the absorption of the dye by the cells. Cells that are “acid-fast” because of the mycolic acid in their cell wall resist decolorization and retain the primary stain. All other cell types will be decolorized. Methylene blue is then used as a counterstain.
What is the purpose of using heat to completely dry a smear after applying bacteria to a slide?
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.
What is the purpose of applying a stain to a bacterial smear?
What is the purpose of applying a stain to a bacterial smear? To provide contrast between the organism and the background. Since bacterial cells are generally transparent, it is very helpful to stain bacteria to provide contrast.
Why is fixing necessary for most staining procedures?
Why is fixing necessary for most staining procedures? ADDITIVE: Mordants are used in gram staining to bind to dye and make it less soluble. For example in staining flagella a mordant is used to thicken the flagella fiber until our eyes can see it. Iodine is mordant.
What are two reasons for heat fixing the smear preparation?
What are the two main reasons to heat fix bacterial smears?
- To kill bacteria on slide;
- to make dye penetrate cells;
- to coagulate proteins of cells thus making cells stick to slide.
What is the purpose of preparing a bacterial smear?
The preparation of a smear is required for many laboratory procedures, including the Gram-stain. The purpose of making a smear is to fix the bacteria onto the slide and to prevent the sample from being lost during a staining procedure. A smear can be prepared from a solid or broth medium.
What is bacterial smear?
A bacterial smear is a thin layer of bacteria placed on a slide for staining. Preparing the smear requires attention to a number of details that help prevent contamination of the culture and ensure safety to the preparer.
Why is heat fixing avoided during the capsule staining procedure?
Do not heat-fix the smear because this can destroy the capsule and will also cause shrinkage of the bacteria, making a clear area around the cell that can mistakenly be identified as a capsule.
What would happen if you heat fix the smear before you air dry it?
Be patient and take the time to let your slide air dry before proceeding with adhering it to the slide. If your slide is wet and you heat fix it, the bacteria will boil and the cellular morphology will be lost.
Why do you have to heat fix a bacterial smear before?
Heat fixing bacterial smears kills the bacterial cells so that they are fixed in place and ready for staining. Heat fixing also adheres the bacterial cells to the slide and allows the sample to take up the stain more easily. Why do you have to do heat fix before doing simple staining and Gram staining?
Why is it important to fix the smear?
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. What would happen if no heat fixing were done?
When to use negative stain or heat fix?
Negative stain is used when viewing bacteria by wet mount or hanging drop slide to view bacterial motility. Heat fixation is not used in negative staining because the goal of the experiment is to view bacteria that has not been distorted by harsh staining or heat fixing. Heat fixing shrinks cells!
How is a smear prepared before staining a microbe?
Before staining and observing a microbe under a microscope, a smear must be prepared. The goal of smear preparation is to place an appropriate concentration of cells on a slide and then cement them there so that they do not wash off during the subsequent staining procedure. Figure 3-4 demonstrates smear preparation.