Gram Staining of Escherichia coli PDF

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Gram Staining of Escherichia coli Introduction: Gram staining is a type of staining for bacteria that allows for an individual to figure out if the bacteria they possess is either gram positive or negative. If the bacterium is gram positive it means that it will retain the crystal violet stain meaning that the bacterium has a thick peptidoglycan in its cell wall. On the other hand, if the bacterium is gram-negative this means that the crystal violet will not stain, and the cell wall has a thin layer of peptidoglycan. Looking at the bacterium Escherichia coli, I predict that it would be a gram-negative bacteria and stain pink because E. coli is found in the gastrointestinal tract. Usually bacteria found in the gastrointestinal tract is gram-negative. Materials: 

Crystal Violet

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Bunsen Burner

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Iodine

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Clothes pin

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Decolorizing Acid Alcohol

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Napkins

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Safranin

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Microscope

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Distilled Water

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Stopwatch

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E. coli bacterium

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Microscope Slide

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Inoculation loop

Methods To start one takes a clean microscope slide and takes an inoculation loop and dip it inside a beaker full of distilled water. Then place the water in the middle of the slide and sterilize the inoculation loop by putting it through the Bunsen burner. Afterwards take the inoculation loop and get a loopful of bacteria and spread throughout the water very thin. Wait for the slide to dry,

then clip it at the end of the slide and wave it through the flame three to five times. Let the slide cool to room temperature and then place one to two drops of the crystal violet stain on the slide. Using a stopwatch let the stain sit for one minute and wash the slide until the excess stain is gone. Next, place one to two drops of iodine on the slide and let it sit for one minute before washing the excess stain off. Then, using decolorizing acid alcohol place another one to two drops on the slide and let it sit for 30 seconds before washing the excess of. Using the last stain, safranin, place one or two drops on the slide and leave it on for one minute before washing off. Afterwards take a napkin and blot dry the slide until all the water is gone and then examine the final product under the microscope. Results: Figure 1 depicts the image that the microscope depicted of the bacterium Escherichia coli staining pink.

Figure 1: Escherichia coli

Discussion: After examining the slide, the results prove that my hypothesis and prediction was correct about Escherichia coli being gram-negative because it stained with a pink color. This is because it has a thin cell wall of peptidoglycan which means that the decolorizing acid alcohol was able to strip away the crystal violet and allowing for the safranin to be able to stain the bacterium....