Microorganism Lab Report

Correctly identifying a microorganism is important in the microbiology lab but also in the medical field. The goal of this project is to use various experiments to identify an unknown bacterium. Culture number eighty-three was randomly chosen and exposed to a series of tests. After these tests were performed it was determined the bacteria is staphylococcus epidermidis.

Introduction To start, the unknown had to be isolated from the mixed culture. Many T-streak plates were performed. Once an organism is isolated, the determination of the organism could begin. The first step in determining what organism was in the unknown tube was to perform a gram stain to determine the morphology of the organism and whether it was gram positive or negative.

I first performed a gram stain to determine whether the organism was gram positive or negative and its morphology. The gram stain resulted in a coccus, gram positive organism that was totally isolated.

After the gram stain was performed, the list of possible organisms was cut down by over 75%. The next test that was performed was then the Nitrate test. After zinc was added the tube turned red. By turning red, the organism has the enzyme, nitrate reductase. Since the unknown turned red, it is certain that it contains nitrate reductase.

After the nitrate reductase test, the field was narrowed down to two organisms. Because two-test elimination is needed, the catalase test was then performed. By having a positive result, the organism has the catalase enzyme. The organism produced many little bubbles when added to the hydrogen peroxide, yielding a positive result.

After the catalase test was performed, it was on track with the previous results, except two of the previously eliminated organisms were catalase positive, putting them back in the possible unknowns. After the catalase test, research was performed to see that by performing the Voges-Proskauer test, it would eliminate the organisms back down to