What are the correct steps in preparing a slide of bacteria for staining?
In order to stain the bacterial specimen for microscopy one must first prepare the smear on the slide. This basically involves three steps—-transferring a liquid suspension of the bacterium on the slide, drying the smear, and then heating slightly to firmly attach the smear to the slide.
Why do you gently heat the slide before staining?
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. After the smear has air-dried, hold the slide at one end and pass the entire slide through the flame of a Bunsen burner two to three times with the smear-side up.
How do you prepare a blood slide?
- Place clean glass slide on a flat surface. Add one small drop of blood to one end.
- Take another clean slide, and holding at an angle of about 45 deg, touch the blood with one end of the slide so the blood runs along the edge of the slide by capillary action.
- Make 2 smears, allow to air dry, and label clearly.
How do you prepare a slide for a smear?
What is the correct order for making a bacterial smear on the slide?
In order to heat fix a bacterial smear, it is necessary to first let the bacterial sample air dry. Then either place the slide in the slide holder of a microincinerator, or pass the dried slide through the flame of a Bunsen burner 3 or 4 times, smear side facing up. Once the slide is heat fixed, it can then be stained.
What should be done first when creating any new smear slide?
What should be done first when creating any new smear slide? Label the slide with the name of the organism.
Why We Do not wipe the slide?
After removing the soapy filling with a clean cloth the surface becomes clean and grease free. If the slide is perfectly clean drop can spread on its surface in a thin even film, otherwise the water collects into small drops and film cannot be made.
What happens if you forget to heat fix your slide?
You forgot to heat–fix your slide. Heat–fixing the slide fixes the bacteria to the slide surface. If this step is not done, the bacteria in the smear would be washed off of the slide during the staining and decolorization steps. You would not see anything on the slide under the microscope.
What happens if a smear is too thick?
If the smear is too thick, proper decolorizing will not be possible. If the smear is overheated during heat fixing, the cell walls will rupture. Cells from old cultures may stain Gram negative even if the bacteria are Gram positive.
What happens if decolorization step is skipped?
During the decolorization step, the gram positive bacteria become dehydrated, trapping the crystal violet-iodine complexes within the multi-layered peptoglycan wall. If you skip this step, gram negative bacteria retain the purple dye. If you decolorize properly, the saffrin dye will dye the gram negative bacteria pink.
How can you tell if you over or under Decolorized?
Remove immersion oil from the smear using xylol. Use appropriate procedures and personal protective equipment when using xylol, since it is a hazardous chemical. If the smear is under–decolorized, repeat the decolorization and counterstain steps. If the smear is over–decolorized, the slide should be stained again.
What are the three key objectives for heat fixing a sample before beginning a staining procedure?
What are the three key objectives for heat fixing a samplebefore beginning a staining procedure? (5 points) the three key objectives for heat fixing a sample are to eliminate thecurrent microorganism then attach microorganisms securely tothe side so they do not become lost during the straining andalso makes the microcosms
What is the difference between doing a simple stain versus a differential stain on a bacterial slide?
What is the difference between doing a simple stain versus a differential stain on a bacterial slide? The simple will only tell you morphological shape and size, while the differential stain will allow for determination of size, shape, and type of the cell wall.
What are the steps for Gram staining?
What is the most important step in any staining procedure?
The performance of the Gram Stain on any sample requires four basic steps that include applying a primary stain (crystal violet) to a heat-fixed smear, followed by the addition of a mordant (Gram’s Iodine), rapid decolorization with alcohol, acetone, or a mixture of alcohol and acetone and lastly, counterstaining with
What is the most important step in Gram staining?
Poor staining technique could lead to inaccurate results. One of the most important steps in Gram staining is the decolorizing step (use of alcohol/acetone). If the decolorizer is not left on long enough, then it will not be able to differentiate between Gram positive and Gram negative bacteria.
Is E coli Gram positive or negative?
The thickness of the smear used in the Gram stain will affect the result of the stain. The step that is most crucial in effecting the outcome of the stain is the decolorizing step.
How do you identify e coli on a culture plate?
Escherichia coli (E. coli) is a Gram–negative, rod-shaped, facultative anaerobic bacterium.
What color is E coli bacteria?
Presumptive identification of E. coli was made based on its characteristic morphology colony on the selective medium MacConkey agar. Rapid lactose fermenting colonies of E. coli appear dry, donut shaped and dark pink in color and are surrounded with dark pink area of precipitated bile salts.
What color is E coli after Gram staining?
E. coli stains Gram-negative because its cell wall is composed of a thin peptidoglycan layer and an outer membrane. During the staining process, E. coli picks up the color of the counterstain safranin and stains pink.
What does an E coli colony look like?
Gram Staining
Coli will appear pink in color. The absence of this (of purple color) is indicative of Gram-positive bacteria and the absence of Gram-negative E.