Escherichia Coli Lab Report

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Bacterial cells are, most of the time, nearly invisible, even under a microscope. This is because they are usually colorless, and for this reason, they must be stained to be properly observed. In this experiment, the class prepared a smear from a bacterial specimen on glass slides and the solution given to stain their bacteria was methylene blue. The bacteria used were Escherichia coli, Bacillus subtilis, and Staphylococcus aureus. Using a microscope, the class was able to successfully identify their features including their arrangements, sizes, textures, and shapes. Materials: • Microscope slides • Agar slant of Escherichia coli • Agar slant of Bacillus subtilis • Agar slant of Staphylococcus aureus • Test tube rack • Inoculating loop x2…show more content…
Next the glass slides were wiped with glass cleaner and kim wipes to rid the slides of any dust particles and smudges. After that, the group used a wax pencil to label each slide: E.C. for Escherichia coli, B.S. for Bacillus subtilis, and S.A. for Staphylococcus aureus. The labels were made on the back of each slide and off-center so that the bacteria could be seen clearly. Once they were clean, 1-2 drops of water were added to each slide. Next, the Bunsen burner was connected to the gas line using the gas hose and ignited with the flint. The fire was made so that there would be a small orange inner flame surrounded by a faint, larger blue flame. Using the Bunsen burner, the inoculating loops were sanitized. This was done by placing the loops’ wires in the fire until they burned bright orange. The group used two so that each could work on a slide simultaneously. After that, they were kept by the flame for about half a minute to stay sanitized as they cooled down. Once they cooled down, the loops were used to carefully collect bacteria, making sure not to scrape the agar slant. To open the slants, the caps were removed and held by the pinky fingers and the tubes were passed through the flame twice once the samples were collected to reduce the chance of contamination. The bacteria were then transferred and spread out in the water on the…show more content…
It is believed to usually be inactive and in spore form but when it is active, though, it is said to produce many enzymes. It is aerobic, which means it does not require oxygen to grow, although it can be anaerobic when nitrates or glucose are present. It is an endospore-forming bacterium, which makes it able to withstand very hot and dry temperatures. It is not considered to be a particularly harmful bacterium to humans as it is not a pathogen. The bacterium was considered to be gram-positive since it stained purple. When observed under the microscope, they appeared to be rod shaped, and arranged in clusters/lines. They seemed to have a smooth texture as
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