(Ziehl-Ne ndid.Eaet Staininn ASSESSMENT critical Thinking and Learning outcomes
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Question
(Ziehl-Ne ndid.Eaet Staininn ASSESSMENT critical Thinking and Learning outcomes Revie 1. What is the difference between a simple and a differential stain? 2. Name the reagent used and state the purpose of each of the following in the Gram stain: a. mordant b, primary stain c, de colonizer d. counterstain 3. Which step is the most crucial or most likely to cause poor results in the Gram stain? Why? 4. Why must young cultures be used when doing a Gram stain? 5. Why was H. neptunium Gram stained? 6. What is meant by "gram variable"? 7. What part of the bacterial cell is most involved with Gram staining, and why?Explanation / Answer
Simple stain - consists of a solution of a single day. Some of the most commonly used dyes are methylene blye, basic fuchsin, and crystal violet. Simple stains allow one to distinguish the shape ( morphology ) of the bacteria. e.g. E. coli and Bacillus subtillus are bacilli or rod shaped bacteria.
Differential Stain - are more complex than simple ones and use more than one stain to differentiate cellular components. They are used to examine structural difference between bacterial groups or to provide contrast to different structures within the same organism.
2.
a. Mordant - A mordant is a chemical that scientist add to a stain to give colour to various organism so they can better identified them. The mordant binds to the chemical dye helping to hold it, so it remains stuck to the organism.
b. Primary stain - is used in Gram staining to detect Gram positive bacteria.
c. Decolorizer - is used to dehydrate to peptidoglycon bilayer, shrinking and tightening it.
d. Counterstain - is a stain with colour contrasting the principal stain, making the stained structure more easily visible.
3.It is the decolorization step which is the Acid- Alcohol ( 3% HCl and 95% ethanol ) and must be timed correctly, the Crystal violet stain will be removed from both Gram positive and negative cells if the decolorizing agent is left on too long ( a matter of second).
4. When gram positive bacteria become too old they stain gram negative.
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