Microorganisms are everywhere. They live on your skin, inside of you, and on every surface you come in contact with throughout the day. For the most part the microorganisms that we constantly interact with cause no harm to us, some even help. However there are always a few that cause trouble to us and when they show up we need to be able to treat them properly. The only way to treat that particular specimen is by knowing what it is as well as its characteristics. This is what our lab was trying to accomplish, identifying a specific organism by using proper aseptic technique to run tests that we used to properly identify our sample.
The first lab consisted of tests to see if the sample was Gram positive or negative, determine what the shape and arrangement, how the sample used oxygen, motility, and if the organism produced hydrogen sulfide or indole. The Gram stain was performed using aseptic technique following the lab manual’s instructions. Once the slide had been heat set and stained, I observed the results of the stain in addition to determining shape and arrangement. The inoculation of the fluid chioglycollate and SIM medium were both completed with sterile procedure while following the handout given by the instructor. In the second lab we got to see the results of our tests from the previous week, which are on the result chart attached. One sample had a small reaction when checking for indole. When adding the drops of Kovac’s reagent to the SIM tube a slight gas was produced but no red ring, meaning the sample is indole negative. The second lab tests were to see if our organism had the enzymes: urease, gelatinase, catalase, or amylase, the ability to ferment lactose and mannitol to produce acid or gas, and the ability to utilize citrate. The inoculations of the urea broth, nutrient gelatin, tryptic soy agar, starch agar, citrate slanted agar, and Durham fermentation tubes were completed using sterile technique while completing the steps in the handout given by the instructor. When coming back for the third lab we were able to see our results from the earlier lab, which are in the result chart attached. Some of the results were extreme, like the nutrient gelatin and the catalase test, while others seemed to have been contaminated, the mannitol fermentation tube. After the nutrient gelatin had been refrigerated for 15 minutes the gel was almost completely liquid, meaning the sample is positive for gelatinase. When adding the hydrogen peroxide drops to the sample the bubbling was quick, rapid, and long lasting. While the lactose tube was a clear negative result the mannitol tube was a slight orange color, making it slightly positive, however this may have been due to an error on my part rather than the sample itself.
The results of the tests, in the attached chart, indicate that my unknown bacterium in this lab was Bacillus subtilis. When looking at the flow chart in the lab manual, Bacillus subtilis can be easily identified with just the gram staining and determining if there are spores in the sample or not, so why would we need to do more testing than that? When trying to identify bacteria there are many types that are similar in shape and Gram stain, leaving a whole world of bacteria clumped together by very basic characteristics that do not help with trying to treat people with the bacteria. The other tests, like the SIM and the Durham fermentation tests, are important for giving more detail to the each dual bacteria and making identification for treatment easier. Each test gives more information about the bacteria’s characteristics so that they can be studied further.
