Over the semester we have learned about different bacteria and how to isolate and test them for certain characteristics. Now we have been given a broth that contains 2 different types of bacteria and we needed to isolate the 2 and find the species of one of our isolated bacteria. For the isolation I started by streaking 3 different types of plates: a TSA plate, a PEA selective plate and a MacConkey's selective plate. These plates help me find that I had two Gram negative plates because nothing grew on the PEA plate that is selective only for Gram positive bacteria. After my Gram stain I concluded that they were also both singular rods. I though I was going to have a difficult time trying to identify one species until I looked at the TSA plate. One of the bacteria gave off a blue-green pigment into the agar, this is only characteristic to one bacterium on the list of specific bacteria we could have. The other bacteria had a cream growth on the TSA plate but a red colony on the MAC plate; this told me that it was not only a Gram negative bacterium, but also one that could utilize lactose. After I isolated both different colonies on slants I decided to identify the bacteria that gave off the blue-green pigment because I had a strong feeling about what it was before the tests. I made a trypic soy broth of the bacteria to run tests with. I started with the Triple sugar iron tests. All those tests gave no change in the broths which was in agreement with my hypothesis on the identification of my bacteria. Next I performed a Nitrate reduction test. The results of this test were also conclusive to my idea: it was negative for nitrite reduction, but positive for denirtifacation. I performed one more test to conformation; this was the Cytochrome oxidase test. The results were positive and my hypothesis was correct, my species of bacteria was Pseudomonas aeruginosa. .
Pseudomonas aeruginosa is part of the Gamma subclass and is an opportunistic pathogen that affects both plants and animals.
