Project: Streak Technique

Decent Essays
I obtained Unknown #518 during the initial project week. To begin our discovery for our unknown, we were instructed by Professor Do to carry out a streak technique on a MacConkey’s Plate for general growth. We also had to do a streak technique onto a Nutrient Agar Plate in order to separate the Gram-Positive microbe from the desired Gram-Negative microbe that we were trying to identify. Before the streak technique was performed, the sample was “vortex” to mix solution, then a loop was sterilized with a flame. The loop was then used to aseptically inoculate a sample from the vial and a lawn was created on the plates, the loop was again sterilized. From the lawn, about 6-8 directional streaks were made using the edge of the loop; then the loop was flamed. The plate was turned slightly to make…show more content…
For the MR Test, 3 drops of Methyl Red Reagent was added to one of the test tubes and the color was observed. The color changed from yellow to red to confirm a MR positive result meaning this microbe could ferment glucose into mixed acids and lower the pH. For the VP Test, 15 drops of VP-Reagent “A” was added and mixed then 5 drops of VP-Reagent “B” was added and color was observed after 10-20 minutes, undisturbing the test tube. The analysis revealed no red top layer, a negative result, which suggests this microbe cannot ferment glucose into acetoin. For the Indole Test, 5 drops of Kovac’s Reagent was added to the green-capped test tube (Figure 5) and the top layer was to be observed. No red layer appeared, another negative result, which confirms that this microbe does not produce indole from tryptophan. The Citrate test tube appears to be positive from Figure 5 since it is blue with growth, however after confirming my results with the instructors, it is a false positive. Thus, this microbe cannot utilize citrate as a sole carbon source and the false positive could have occurred from contamination or another unknown
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