Gram Staining Data Interpretation Please type the answers to the following quest
ID: 282076 • Letter: G
Question
Gram Staining Data Interpretation Please type the answers to the following questions below (double spaced) and attach the data collection sheets when you hand in this lab report. hy do some cells stain gram positive and some stain gram negative? Explain. 1. W 2. Did your results agree with the published information (in other words look up the bacterial strains and find out if they are gram positive or gram negative)? If not, where do you think you might have made an error? 3. Suppose you are viewing a sample from a PURE culture and observe both red and purple cocci. What are the possible problems that woul cause such an inconclusive result? 4. Since you cannot identify bacteria based on a Gram stain alone, why might a physician perform a Gram stain on bacteria taken from a patient's infection? 5. What is the purpose of Gram's Iodine? Alcohol? 6. Why is it necessary to counterstain?Explanation / Answer
1. Gram staining of bacteria is used to differentiate between gram positive and gram negative bacteria. As the gram positive cell has thick cell wall containing peptidoglycan, it can retain the gram staining colour and as a result appear as purple. On the other hand gram negative bacteria has thin cell wall and can not hold the purple colour and appear as pink in staining.
2. Bacillus subtilis is gram positive.however they appeared as gram negative. There could be several reasons which might have gone wrong. Such as-
i) In the iodine fixation step is ommited, as a result the crystal violet dye is not fixed.
ii) Decourization step is performed for longer times, which might washed away the crystal violet stain.
3.As this is a pure culture, there is no chance of mixing gram positive and negative bacteria. If the sample is old, then part of it may retain the purple colour and part may loose the stain and appeared as red.
4. Gram stain alone is not sufficient to identify the bacteria, however it can differentiae between gram positive and negative bacteria. Based on this saining results, a physician can make his treatment plan further. Thus it is important to know for the physician which type of bacteria it is before going further treatment options.
5. Grams iodnie is used to fix the crystal violet colour, so it will not wash wawy easily with decolourization step. Alcohol is used for decolourization.
6. As the gram negative bacteria loose the crystal violet colour they might be not easily detectable under microscope. Counterstain thus used to stain the gram negative bacteria in pink so they can easily visible.
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