microbiology unknown lab report samantha moellenhoff microbiology, fall 2012 introduction with the constant debate in society about microorganisms, it is important to distinguish their identities. There are many reasons as to why this is important such as knowing what agent is causing a disease and the correct treatment is determined, to knowing which microbes are beneficial to a person and important to body functioning. The purpose of this study was to identify an unknown bacterium by applying all methods that were previously conducted and learned in the microbiology laboratory class.

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materials and methods an unknown test tube labeled 120 was given out by the lab instructor. The goal at this point was to determine two separate unknown bacterium, one gram positive and one gram negative. The procedures performed consisted of sterile technique in addition to being followed as stated in the referenced course laboratory manual, unless otherwise noted. The first procedure performed was an isolation of the unknown bacteria with the goal of obtaining a pure culture. This was conducted by streaking the unknown out on a trypticase soy agar tsa plate using the t streak method described in the manual.

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It was critical to follow each step correctly while using sterile technique because from this test not only is the stain determined but also the shape of the cells. Culture a was determined to be a gram positive cocci and culture b was determined to be a gram negative rod. The biochemical tests performed were chosen based on the identification table that was given from the lab instructor. The flow charts on the following page list these tests and results for the gram positive and gram negative bacteria. The bacterium was grown on a tsa agar plate for use of additional tests, gram stain reaction determined that the unknown was a gram positive cocci. The growth and color change to yellow indicated mannitol fermentation because acid was produced. This indicated that the unknown was either staphylococcus aureus or enterococcus faecalis.

Acid fermentation is a characteristic of pathogenic staphylococci. then, a nitrate broth test was performed. The catalase test had a positive reaction meaning the bacteria produced the enzyme catalase confirming that the unknown bacterium was staphylococcus aureus. staphylococcus aureus is in the staphylococcaceae family. It is usually found in nasal passageways but can also be found on skin, in the oral cavity and gastrointestinal tract.

staphylococcus aureus is commonly known because of mrsa methicillin resistant staphylococcus aureus which is an epidemic in the medical world because of its antibiotic resistance. s aureus can become pathogenic through tissue invasion and toxin pollution. Vancomycin is the antibiotic usually prescribed because of resistance to penicillin.

mcdonald, v. Retrieved december 3, 2012 unknown number 118 jennifer mills april 30, 2013 microbiology, bio:203.604 introduction in the past, it has been vital to distinguish the identities of microorganisms in the world.

Knowing their identity has aided in diagnosing numerous diseases and has discovered the most beneficial treatment. the purpose of this study was to identify a gram positive and a gram negative bacterium from a mixed culture. the methods that were previously studied and practiced in the microbiology laboratory class were applied in order to identity two unknown bacterium. matrials and methods the lab instructor gave out a test tube labeled number 118, which consisted of two unknown bacteria, one gram negative and one gram positive. Sterile techniques were followed while performing precise instructions as stated in the referenced laboratory manual.

The first procedure performed to isolate a pure culture from the mixture in the test tube onto a solid media. A sterile inoculating loop collected bacteria from the test tube with the unknown, and streaked a series of zigzag lines along two nutrient agar plates, using the quadrant streak method. Both plates were studied, noting their characteristics, which were recorded in a journal. The gram stain procedure was carefully followed according to the referred laboratory manual. The glass slide and nutrient agar plate were labeled gram negative and were then stored in the refrigerator. In order to identify the gram positive bacteria, a sample from the original test tube was streaked on a mannitol salt agar plate and placed in the incubator at 37 degrees celsius. Several biochemical tests were chosen based on the identification table which was given by the lab instructor.

These tests and results were recorded on the flow chart and the tables on the following pages for the gram negative and gram positive bacteria. All of the following tests were performed on these unknowns: example of a microbiology unknown lab report by taylor autry in this paper i will discuss the processes of how i came to find my two unknown bacteria. In the medical field bacteria and infections of different kinds are the core of the practice. These bacteria must be able to be identified in order to treat patients properly, efficiently and safely. materials and methods: the unknown number 123 handed out by the professor on march 20, 2014 contained both a gram positive bacteria and a gram negative bacteria. At this point everything that had been learned in microbiology lab and that had been explained in our lab manual 1 was put into action.

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The streak method was used to spread the bacteria across the nutrient agar in hopes of isolating a pure culture of one of the bacteria. In order to do the streak method, an inoculating loop was sterilized with a bunsen burner and put into the unknown specimen. Upon returning and observing the streak plate, there was an abundance of green across the plate. After observation, a sample was taken from the isolated colony on the streak plate and another streak plate was done with that, trying to further isolate the colonies. As well as using the quadrant method to further isolate the colonies, a sample was taken from the best colony on the original streak and gram stained.

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To decipher between which biochemical tests to perform, the gram positive and negative tables handed out by the professor, were referred to. From previous biochemical tests done in the semester, pseudomonas aeruginosa was already suspected because of the green pigment of the original streak plate. Upon reviewing the identification tables, the deciding biochemical test was the casein test which tests for the production of the enzyme casease to break down the milk protein casein. After observation there was a clear positive result, which showed the bacteria produced casease.