Day 4 - Effect of UV Light Sterilization

There are different ways to sterilize things.  One way is through UV light radiation. 

Materials:
2 agar plates
Beaker of about 300 mL distilled water
UV light wand
4 different kinds of unknown bacteria in broth cultures from our four lab groups
Pipets with disposable sterile tips





Steps:
1.  Label the agar plates.  On one write "before" and on the other write "after."

2.  Inoculate the "before" agar plate with the distilled water.

3.  Using pipets, put 5 microliters of each kind of bacterial broth in the beaker of water.  Mix well.  Dispose of the pipet tips in the biohazard waste bag.


4.  Use the UV wand to sterilize the water.  The wand is automatically set for the correct amount of time for the amount of water we have.



5.  Inoculate the "after" agar plate with the sterilized water.

6.  Incubate the two agar plates at 35 degrees for 24 hours.

7.  Observe results.







Results:  No bacterial growth on either agar plate.

Discussion:  Neither agar plate had bacterial growth.  For the "after" sterilization, this is because the sterilization worked, killing the bacteria.  For the "before" agar plate, there is no growth because we used distilled water, which has no bacteria in it.  We had intended to use normal tap water for the "before" agar plate, which would likely have had bacteria in it.  It is Steubenville, after all.  The city is not exactly known for clean water.  If we had used tap water, we would probably have gotten colonies on the agar plate.  But we did not get colonies because we used distilled water.