Decent Essays
Unknown Experiment Introduction: The purpose of this experiment is to distinguish and indentify an unknown bacterium. There are several tests that can help one eliminate and narrow down the options. The most useful test, and the very first one done, is a gram stain. This test will tell whether the bacterium is gram-positive or gram-negative. After the type of gram stain is identified, the tester has a wide array of differentiating tests at their disposal. Based on the results from these tests, and the numerous others that are available, one can accurately establish the identity of an unknown bacterium. Materials: 1-Tube containing unknown bacteria, crystal violet, iodine, decolorizing agent, Safranin, Bunsen burner,…show more content…
4.) To further differentiate the bacteria from other options, obtain 1 TSA plate and perform a bacitracin susceptibility test. 5.) Inoculate the plate with a lawn coverage streak and place 1 bacitracin antibiotic disk in the center of the plate. 6.) Incubate the plate, right side up, at 37 C for 24-48 hours. 7.) Record the results from the bacitracin test. 8.) Combine the results and information from the previous tests and establish the identity of the unknown bacteria. Results: Test Result Gram Stain Purple, gram-positive cocci in chains Morphology Cocci (in chains), lancelet-shaped and slightly curved Hemolytic Test Alpha (Partial Clearing, Green) Bacitracin Susceptibility + (Susceptible) Conclusion and Background Information: The gram stain test was able to identify the bacterium as a gram-positive organism, and the morphology distinguished it as a strain of streptococcus, and these finds helped direct the other tests. Hemolytic tests are very useful in differentiating specific species of a certain family of bacteria. The hemolytic test showed the bacterium to be of alpha clearing, which meant it only partially lysed the red blood cells and left a greenish tint. This identified the bacterium as either strep pneumoniae or faecalis. The bacitracin test, which tests whether the bacterium is susceptible to the antibiotics in the disk, posted a positive
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