Isolation of Bacteria Essay

The purpose of the lab is to apply what has been learned so far in Microbiology, and use it to collect and examine microbial species from the physical environment.

The physical environment around the lab will be utilized to find out the variety of different microbial species growing in and around the lab. This investigation will help in preparation for the individual projects that will be done at the end of the semester. Materials and Methods: The lab chosen was Exercise 24: Isolation of Bacteria in our Physical Environment.For this lab, four TSA Petri plates, a test tube of sterile water, and sterile cotton swabs were obtained.

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The Petri plates were labeled 1-4. Plate number 1 was left on the lab bench for the duration of class. It was labeled “air sample”. Plate number 2 was divided in half, side 1 contained the steering wheel sample, and side 2 contained the cell phone sample. Plate number 3 was also divided in half, one side was labeled 3, which contained the sample from the door handle on the women’s restroom. The other half, labeled 4, contained the sample from the button on the pop machine.

Plate number 4 contained the sample from a dollar bill. To obtain the samples, the sterile cotton swab was dipped into the test tube containing the sterile water, it was then swabbed onto the surface being tested. Then the cotton swab was streaked out into one section of the Petri plate. The cotton swab was then thrown in the trash. The bacterial loop was then used to make the second and third streaks on the plate. After each streak, the loop was sterilized in the Bunsen burner. The lid was then replaced onto the Petri plate, and was moved to the incubator for 48 hours at 35 degrees Celsius.

The same procedure was used on all of the samples. Following the 48 hour incubation period, the Petri plates were observed for colony morphology, and the results were recorded. A Gram stain procedure was conducted to find out if the species were Gram-negative or Gram-positive. The results of the Gram stain were observed under the microscope and the results were recorded. Results: The colony morphology of plate 1, the air sample, contained six small, shiny colonies.

There were two yellow in color and four were a cream color. They were opaque and elevated.The Gram stain was positive, so the cells turned a violet color.

They were round cocci growing in clusters. The controls used for all of the Gram stains were Bacillus subtilis and Escherichia coli. On plate 2, the half labeled 1, containing the steering wheel sample, contained many yellow circular colonies that were shiny, opaque, and elevated. The half labeled 2, containing the cell phone sample, had many yellow circular colonies that appeared shiny, opaque, and elevated. The Gram stain procedure was done with the cell phone sample, the result was Gram-negative bacilli, some of the bacilli were growing in chains.Plate number 3, side number 3, which contained the sample for the door handle of the women’s restroom, showed yellow circular colonies. They were shiny in appearance, and were elevated. A Gram stain was conducted for this sample, the results were Gram-negative bacilli.

The half labeled number 4, contained the sample from the pop machine. It had many yellow circular colonies that were elevated, and shiny in appearance. Plate number 4, containing the sample from the money, had many yellow circular colonies. They were shiny in appearance, and also elevated.A Gram stain was conducted for this sample, the results were Gram-negative bacilli. Summary of Results SamplesColony MorphologyCellular MorphologyGram Stain Air SampleYellow and Cream color, elevated, shinyClusters of cocciGram-positive Cell Phone SampleYellow, shiny, elevatedBacilli, some growing in chainsGram-negative Door Handle SampleYellow, shiny, elevatedBacilliGram-negative Money SampleYellow, shiny, elevatedBacilliGram-negative Summary of results for isolation of bacteria in our physical environment Conclusion: All of the colony morphology on the Petri dishes were the same, except the air sample.The air sample did not have very many colonies growing on it, but it had noticeably different species growing on it. The different types of microbes growing on the air sample shows that there can be many different kinds of microbial species present in one area.

One thought that came to mind is, the air sample was never touched by a person, it was just left sitting out for the class period and then the lid was replaced. The other three plates contained samples from surfaces that people had touched with their hands, which could be one reason the air sample did not look like the other three plates.

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