1) Why is the gram stain technique more valuable than the simple stain technique
ID: 32296 • Letter: 1
Question
1) Why is the gram stain technique more valuable than the simple stain technique in a diagnostic laboratory? Under what circumstances might the simple stain be preferable to the Gram stain technique?
2) Suppose a student research for the alcohol bottle for the decolorization step and instead took the bottle of distilled water. What would be the color of a gram-positive and a gram-negative bacterium at the conclusion of the procedure? Explain thoroughly.
3) How might the Gram stain technique be of value in establishing the purity of a culture of bacteria?
Explanation / Answer
1.The gram stain has two dyes. There are two types of bacterial cell walls-gram positive which is very thick and gram negative which isn't as thick. The gram positive wall holds onto crystal violet for longer than gram negative which can be destained. Then the gram negative are counterstained with a second dye. This allows you to break all bacteria down into two basic groups and allows to begin the identification process. Simple staining only uses one dye. If all you want to know is what shape the bacteria is or if there is bacteria at all, a simple stain is quicker to do.
2.The same color, as the gram negative bacteria would not have enough stain washed away to assume their lighter shade. Remember, the thickness and construction of the peptidoglycan that forms the walls of the two types of bacteria varies significantly. Gram positive bacteria have the single, thick wall. Gram negative have a thinner and double wall that does not retain the stain as well.
3. If all of the cells in a culture are Gram positive, this would tell you that there are no Gram negative cells in the culture. But you must do many additional test like cell morphology, colony morphology, sugar fermentation tests plus other tests in order to conclude that it is a pure culture.
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