1) Identify the steps taken in the preparation of a bacterial smear to prevent c
ID: 31952 • Letter: 1
Question
1) Identify the steps taken in the preparation of a bacterial smear to prevent contamination of the culture and yourself working with a bacterial smear?
2) Summarize the "fundamental theory" of simple staining. hint: what scientific property allows the dyes t bind the bacterial cell wall?
3) What would happen if you placed a large drop of water on a slide rather than a loopful, when preparing a bacterial smear?
4) Discuss the possible outcomes if an air-dried smear were not heat fixed before proceeding to the staining step.
5) While viewing a slide of a "pure" culture you observe two different shaped bacteria; some rod shaped while others are spherical. How could this happen? List at least two explanations and/or sources for this result.
Explanation / Answer
1)
The steps taken in the preparation of a bacterial smear to prevent contamination of the culture are:
2)
Principle of simple staining: The acidic species that are present on the cell wall of bacteria binds with basic dyes like safranin, crystal violet and methylene blue, etc.
3)
If you placed a large drop of water or saline on a slide rather than a loopful, when preparing a bacterial smear, then during heat fixing the boiling of water boils rapidly and spills from the slide. So, bacteria would not stand on the slide for observation.
4)
The possible outcomes if an air-dried smear were not heat fixed before proceeding to the staining step are:
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