Making a Gram Stain shows us if the bacteria cell wall is negative or positive which indicates the structure of the cell wall. Gram positive cell walls are thicker and have a bigger layer of peptidoglycan and teichoic acid and lopoteichoic acid molecules while gram negative cell walls are thinner due to a smaller layer of peptidoglycans, but have a complex layer of lipd macromoecules. Medically it is important to know if the cell wall of a bacteria is possitive or negative because gram negative bacteria are usually more resistant to antibiotics due to thier cell wall structure.
Two dies are used in the gram stains, Crystal Violet and Gram's Iodine. The Crystal Violet is added first, then rinsed with ethanol and then stained again with Gram's Iodine. The concept behind this is that because a gram positive cell wall is larger it will pick up the crystal violet stain while gram negative's cell wall is too small to hold the die. When we rinse the slides with ethanol, if the stain did not absorb into the cell wall it will be rinsed off allowing the next stain, gram's iodine to stain it. If the bacteria is gram positive it will already be fixed with the red crystal violet and will not have room to pick up the purple gram's iodine and will remain red. The gram negative bacterial will stain purple because they did not have room in their cell wall to pick up the crystal violet stain and it gets washed off.
Results:
Unknown bateria is Gram Positive.
Environmental #1(Lauren) is Gram Negative.
Environmental Sample #2: Gram positive
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| Lauren's Environmental Gram - Stain |
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