Lab Assignment MCB2010C – Dr. McPartland

Question

Student Name: Oscar Manuel Gonzalez

A researcher wanted to test the effectiveness of a new antibiotic on Streptococcus pyrogenes, the species of bacteria that causes strep throat. Bacteria were added to dish 1, dish 2, and dish 3. A disk soaked in the new antibiotic was then placed in dish 2. Dish 3 was set up as the
control. The dishes are shown in the diagram below.


59 State one appropriate hypothesis for this experiment. [1]

One appropriate hypothesis for this experiment could be: The new antibiotic will inhibit the growth of Streptococcus pyrogenes in dish 2, resulting in a zone of inhibition around the antibiotic disk

60 All three dishes were placed in an incubator at 37°C for 24 hours. The results for dish 1 are shown to the right.

Complete (color in) the diagram of dish 2 below to represent an example of experimental results that would support your hypothesis. (Use the “Draw” tab in Microsoft Word)

Explain how your diagram supports your hypothesis. [1]
The clear zone (zone of inhibition) around the antibiotic disk in dish 2 indicates that the antibiotic is effective in killing or inhibiting the bacteria, thus supporting the hypothesis that the new antibiotic can inhibit the growth of Streptococcus pyrogenes.

61 Describe how the disk in dish 3 should be prepared so it can serve as the control for
this experiment. [1]

The disk in dish 3 should be prepared by soaking it in a solution that does not contain the new antibiotic, such as sterile water or a different type of non-antibiotic substance

Answer 1

62 Explain the significance of having a control dish (dish 3) in this experiment. [1]

The significance of having a control dish (dish 3) in this experiment is to provide a baseline comparison for the results observed in dish 2. The control dish allows the researcher to determine whether any observed effects on bacterial growth are due to the new antibiotic or other factors, such as the natural growth of the bacteria in the absence of the antibiotic. By comparing the growth pattern in the control dish to that in the dish containing the antibiotic, the effectiveness of the antibiotic can be accurately assessed.