Purpose: The purpose of this lab is to discover substances that can slow the growth of, or kill, microorganisms.
Hypothesis: The antiseptic that will prevent the growth of bacteria the most is iodine. The disinfectant that will prevent the growth of bacteria the most is bleach. Procedure:
To begin the lab, turn the agar plate over and divide the plate into four quadrants and label the agar plate whether you used the E. coli or B. megaterium and number the quadrants 1 through 4. Please keep in mind that one pair will test the E. coli and Environment 1 or 2, and one pair will test B. megaterium and Environment 1 or 2. After, you will need to swab the E. coli and B. megaterium on two different nutrient agar plates using a sterile disposable inoculating loop. Remember not to dig in into the agar or the agar might break. Then, you will choose two environmental samples (rat, turtle or fountain) and do the same steps you used for the E. coli or B. megaterium. When you have swabbed all of the agar plates with E. coli, B. megaterium, Environment 1, and Environment 2, then you will choose two disinfectants and two antiseptics. Then you will use the forceps to pick up a paper disk and soak it in the antiseptic and place it in quadrant one and repeat this step with the second antiseptic for quadrant two. Then you will repeat these steps with the disinfectants, but place the disinfectants in quadrants three and four. After all the steps have been completed for all four agar plates, incubate the plates upside down at 37 °C for 48 hours. Observe the plates after 48 hours of incubation and use a millimeter ruler to measure the diameter of the clear zone surrounding each paper disk. Record the measurements on the data table and trade with the other pair to obtain their information too. Results:
Table 1: Distance from the antimicrobial agent to the bacteria. QuadrantAntimicrobial