Gram Unknown Lab Report

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In order to determine the identity of two unknown bacteria, I performed a series of experiments over several days. To begin this process I created a dichotomous key that I utilized as a guide to perform a series of inoculations, while using both selective, and differential media. The series of inoculations eliminated bacterium based on test results until the correct bacteria were both positively identified. On day one of this process I received two bacteria, one labeled 7A and the other labeled 7B. I began the experiment with thirteen possible bacteria. The thirteen possible bacteria included, Enterococcus faecalis, Bacillus subtilis, Bacillus megaterium, Staphylococcus aureus, Staphylococcus epidermis, Micrococcus roseus, Micrococcus luteus, …show more content…
In order to determine this I performed a gram stain on each of the bacteria. I observed each bacterial slide on a microscope under 1000X resolution. The bacterium labeled 7A showed multiple staphylococcus arrangements that were stained red. I determined that this bacterium was gram negative because of red color of the bacteria. The bacterium labeled 7B showed multiple single bacilli that were stained purple. I determined that this bacterium was gram positive because of the purple color of the bacteria. By performing the gram stain, I was able to divide my two bacterium into 1 gram positive bacterium, and 1 gram negative bacterium. I was now able to determine that bacterium 7A could only be one of the gram positive bacteria. The gram positive bacteria where E. faecalis, B. subtilis, B. megaterium, S. aureus, S. epidermis, M. roseus, and M. luteus. Additionally, I was also able to reduce the possible bacteria for 7B to one of the gram negative bacteria. The gram negative bacteria included, P. vulgaris, E. coli, C. freundii, E. aerogenes, A. faecalis, and P. …show more content…
I performed this inoculation in order to identify whether the unknown bacterium was able to ferment the carbohydrate Mannitol. After 48 hours of incubation, the result of bacterium 7A was positive for Mannitol fermentation. I was now able to determine that bacterium 7A could only be a bacteria that would test positive for Mannitol fermentation. The possible bacteria were then reduced to E. faecalis, B. subtilis, B.megaterium, and S. aureus. With this result I was also able to eliminate S. epidermis, M. roseus, and M. luteus. Additionally on day one, I inoculated bacteria 7B onto a Urea tube of media in order to further eliminate incorrect bacteria. The Urea tube would distinguish if bacterium 7B would produce Urease, resulting in a positive test result. After 48 hours of incubation, the result of the Urea agar slant was positive. This result reduced my possible bacterium’s identity to bacteria that would produce a positive result in a Urea agar slant. The possible bacteria were P. vulgaris, C. freundii, or P. aeruginosa. I was then able to completely rule out E. coli, E. aerogenes, and A. faecalis as possible

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