The Effect Of Extreme Freezing On Bacteria Science Fair Projects

Tips for Freezing Bacteria Science Fair Projects

For this science fair project you will need a microscope and access to different freezing apparatuses. It is important to make observations about your bacteria when it is not frozen in order to generate control data, or baseline data. You will then use this data to make comparisons with your frozen data.

PURPOSE

The purpose of this experiment was to determine how extreme freezing would affect the subsequent growth rate of bacteria.

I became interested in this idea when my dad started freezing different types of commercial food at different freezing levels and getting different results.

The information gained from this experiment could help scientists and doctors understand how freezing bacteria can be helpful.

HYPOTHESIS

My hypothesis was that the colder the temperature, the fewer the bacteria colonies would subsequently be.

I based my hypothesis on the fact that freezing will stop bacteria growth for a while.

EXPERIMENT DESIGN

The constants in this study were:

• The testing procedure
• The time the bacteria is frozen
• The amount of bacteria
• The way they were measured after freezing
• The two types of bacteria
• The same vials the bacteria was in
• The temperatures are always -60, -30, -20,and -10 degrees Celsius

The manipulated variable was the different freezing levels.

The responding variable was the colony growth.

To measure the responding variable in this experiment, I counted the bacteria colonies.

MATERIALS

PROCEDURES

1. First, gather the following bacteria on day 0.
a. Escherichia coli
b. Staphylococcus aureus
2. Next, make suspension for the bacteria.
3. Divide the bacteria between 20 vials, with 200 micro-liters per vial.
4. Label the vials.
a. Label five vials, S V. 1, V. 2, V. 3, V. 4, and V. 5 -20 Celsius
b. Label five other vials S V. 1, V. 2, V. 3, V. 4, and V. 5 - 30 Celsius
c. Label five other vials S V. 1, V. 2, V. 3, V. 4, and V. 5 - 60 Celsius
d. Label the five remaining vials S V. 1, V. 2, V. 3, V. 4, and V. 5 -10 Celsius
5. Repeat step 4, but label the vials with an E instead of an S for Escherichia Coli
6. Freeze the bacteria at the four temperatures,
-20 Celsius
-30 Celsius
-60 Celsius
-10 Celsius
7. On day one, take vial one out, thaw, and let it sit for 10 min. at room temperature.
8. Refreeze vial one.
9. On day two take out vial 1 and 2, thaw, and let it sit for 10 min. at room temperature.
10. Refreeze vial one and two.
11. Repeat steps 6-7 with vials 3, 4, and 5.
12. On day six, thaw all the bacteria
13. Pipette 10 micro-liters to a blood agar plate.
14. Spread the bacteria with inoculating loop over the surface of the blood agar plate.
15. Incubate bacteria overnight at 37 degrees Celsius
a. Do a colony count.
16. Destroy bacteria in autoclave-using hospital’s procedures.

RESULTS

The original purpose of this experiment was to determine how extreme freezing would affect the subsequent growth rate of bacteria.

The results of the experiment were that the colder the temperature the bacteria were kept frozen, there were less bacteria colonies.

CONCLUSION

My hypothesis was that the colder the temperature, the fewer the bacteria colonies would subsequently be.

The results indicate that this hypothesis should be accepted

Because of the results of this experiment, I wonder if there would be a difference if I froze different types of bacteria.

If I were to conduct this project again, I would do a couple of things differently. First, I would try different types of bacteria. Second, I would try different freezing levels. Third, I would freeze them longer. Fourth, I would incubate more blood agar plates of plates. 3rd party credit