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Petri Dish Lab

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Introduction The purpose of this experiment was to apply all knowledge gained from the entire semester while in the lab and apply it to be able to identify an unknown genus and species gram positive bacteria. Each student was given a petri dish with an unknown Gram positive bacterium inside. The petri dish with the unknown gram positive bacteria that was used in my experiment was #8. The possible bacteria inside my petri dish could be any of the following: Bacillus subtilis, Bacillus cereus, Mycobacterium species, Corynebacterium species, Lactobacillus, Staphylococcus aureus, Micrococcus luteus, Staphylococcus epidermidis, Enterococcus faecalis, Streptococcus pyogenes, and Streptococcus pneumoniae Hypothesis I predicted that the bacteria …show more content…

Under the microscope, I was able to observe a purplish blue tetrad looking Cocci clustered together. The results for the Catalase test was an instant bubbling that turned into a bubbling over effect on the bacteria on the glass slide. This indicated a positive reaction for catalyst. The results for the MSA were negative for mannitol fermentation. There was no change in the agar and the colonies remained translucent. Finally, the results I obtained from the oxidase test were also negative. The oxidase reagent test strip had no change in color happen at all, indicating a negative …show more content…

The first test conducted was a Simple stain. This allowed me to be able to differentiate whether I had a Cocci or Rod shaped bacteria under the microscope. It also allowed me to know which test I showed go to next. The second procedure conducted was the Catalase test. This test was to check for the presence of the catalyst catalase which liberates molecular oxygen. This catalyst is necessary for an aerobic organism to survive in aerobic conditions. After the experiment it was observed that my Gram positive organism did in fact bubble and utilize catalase. The third test conducted was on the MSA agar. This test was conducted for the purpose of selective and differential whether or not my organism can tolerate high salt concentrations. It is based on the mannitol fermentation. The phenol-red indicator helps to identify the bacteria. Upon viewing my results it was determined that my colonies did not ferment mannitol. This was easily observed because they remained translucent. The incubation times for all of the inoculated tests were for 48 hours (due to lab schedule, supposed to be 24 hours) and the temperature they were incubated at was at 37C. 37C is the optimal temperature to maintain the state of the agar as well as the ideal temperature for continued microbial growth to occur. My fourth and final test conducted to help identify my bacteria was an Oxidase test. This test

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