Gram Stain Lab Report

When finding out unknown bacteria you have to go through several steps to figure out what it could be. I was given unknown bacteria number 28 and asked to run different testing to identify exactly what this bacterium is. I ran 6 test to determine my unknown. These test includes: Gram Stain, SIM, Sucrose, Citrate, MAC, and EMB. Each one of these test are different and they will give a positive or negative feedback which is how we will know which bacterium I have. A gram stain is one of the most use stain in microbiology. The purpose of a gram stain is to divide microorganisms into gram positive or gram negative. In this procedure you will use Crystal violent, Iodine, Acetone, and Safranin. You use different dyes because Gram negative microorganisms have a higher lipid content and it’s soluble in acetone whereas gram positive microorganisms are less permeable after acetone and the crystal violet-iodine becomes trap inside the cells. When preforming this test or any other test it’s important to use your inoculating loop and …show more content…
This medium is a selective and differential medium designed to isolate and differential enteric based on their ability to ferment lactose. Lactose-fermenting organism grow as pink and non-lactose fermenting organisms grow as colorless or clear colonies. My medium turn yellow which means it’s non-lactose or negative for lactose. Please refer to Figure 6 to see an example. EMB is my last test I performed which is also a plating medium and EMB stands for Eosin Methylene Blue Agar. This medium is also selective and differential and very similar to MacConkey Agar. The combination of the two dyes inhibits most gram positive bacteria but allows many gram negative organisms to grow. Colored colonies mean the bacteria is lactose fermenter and colorless colonies means non-lactose fermenter. My results shown in Figure 7 did not change color although you can see where I streak the

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