The Observation of Bacteria in Pond Water, Cheek Cells, and E. Coli, S. Aureus, M.smegmatis under Compound Light Microscope by Using Staining Technique

Topics: Escherichia coli, Gram-negative bacteria, Bacteria Pages: 6 (1400 words) Published: September 28, 2014
The Comparative Analysis of Simple Staining and Gram Staining Techniques by observing E. Coli and S. Pyogenes under the Compound Light Microscope


A German bacteriologist, Dr. Theodore von Escherich, was the first man in 1885 who discovered the bacterium named Escherichia coli, which are gram negative and appears in rod shaped. Most kind of bacteria E. Coli does not cause diseases and some strains indeed are beneficial in helping the process of food breaking down in the intestines. However, “the most infamous strain E. Coli O157:H7”, which caused the outbreak of Jack in The Box hamburger in 1993 and the recent spinach outbreak in 2006, spread out abdominal pain and diarrhea on the civilization (American et al., 2011).

Streptococcus pyogenes is a spherical, gram-positive bacterium, which was discovered by Hippocrates, who was known as “Father of Medicine” in the fifth century B.C. (Leyro et al, 2008). Streptococcus pyogenes affects its hosts in many different ways and causes large ranges of diseases, which includes both mild and serve disease, such as such as fever, severe pain, dizziness, and red rash. S. Pyogenes can destroy both red blood cells and white blood cells, which is responsible for being immunization (Todar et al, 2012).

Both of bacteria, E.Coli and S. Pyogenes, were observed under the compound light microscope, which is a type of microscope using visible light and a system of lenses to magnify the images. In this second lab experiment, four slides of bacteria were viewed under the compound light microscope from 40X up to 400X total magnification for the purpose of giving the images of bacteria in detail beautifully.

Moreover, the most important part of the experiment was the studying of being familiar to the two primary staining techniques, which were simple staining and gram staining. In the simple staining technique, the chemical methylene blue helped penetrating the cell wall and allowed the cell to be visible. Last but not least, the second staining technique, the gram staining, was beneficial on separating the bacteria into gram positive and gram negative under the compound light microscope. Especially, the technique of heat fixing killed the organisms without serious distortion, so their adherence would improve to stick on the slide and also took up dye more easily.

In this study of the lab experiment, the improvement of the knowledge of using simple staining and gram staining is beneficial in the study of microbiology in the future. The ability of distinguishing the difference between gram positive and gram negative bacteria by using gram staining technique also serves as a potential object to understand and discover more about all the bacteria in the world.


Materials: The compound light microscope, bibulous paper, methylene blue, crystal violet, iodine solution, ethanol solution, safranin, E. Coli, and S. Pyogenes samples were provided by the biology department of Texas Southern University.

Methods: The E. Coli and S. Pyogenes were scratched on each two slides and heat-fixed on the Bunsen burner. In simple staining procedure, two slides of E. Coli and S. Pyogenes were covered with methylene blue, rinsed with water, and observed under the compound light microscope up to 400X total magnification. In gram staining procedure, the remained two slides of E. Coli and S. Pyogenes were covered with crystal violet in one minute then washed off with water gently. Obtaining iodine solution to cover two slides for another one minutes the rinsing with water again. Using ethanol solution to decolorizing the bacteria in the slides then rinsing with water immediately. Lastly, the safranin stain was applied on two slides for another one minute before rinsing with water. After drying gently the two slides with bibulous paper, the E. Coli, and S. Pyogenes samples were observed under the compound light microscope with magnification up to 400X....
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