90 EXERCISE RESULTS 14 NATI Observations and Conclusions Questions 1. Explain wh
ID: 141760 • Letter: 9
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90 EXERCISE RESULTS 14 NATI Observations and Conclusions Questions 1. Explain why crystal violet, a basic stain, would not be useful in the negative stain technique What are the advantages of 1) the negative stain technique over the simple stain technique and 2) the simple stain technique over the negative stain technique? 2. 3. Suppose a clean slide were used for this exercise and still a number of unexpected bacteria appeared in the finished smear. What might be their source? 4. Why aren't bacterial smears heat fixed when performing the negative stain technique? Compare the size of an organism observed after negative staining with the size of the same organism stained by the simple stain technique. Explain the reasons for any differences. 5.Explanation / Answer
1.Crystal violet would not work because as it is basic stain it is positive so that it would bind to the bacteria and you would not be able to see the bacteria
2.Advantages of negative stain over simple stain
No heat fixation so bacteria do not shrink able to get size
Spiralchette is seen
It shows the presence of capsule as negative staining highlights the background without touching the specimen
Advantages of simple stain
Faster process
Less change of contamination heat fix
Easy to observe morphology and size and shape
3.contamination may be from the air from the air borne bacteria or from the water you have cleaned with
4.generally heat fixation is done for killing bacteria ,or for penetration of stain or to fix cells to slide so that they cannot wash away
Heat fixation cause cells to shrink
In negative staining we don’t heat fix because the goal of the experiment is to view bacteria that has not been distorted and shrinked so that cell shape and size are not distorted and are accurately observed and useful to view delicate structures like capsule
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