|MadSci Network: Cell Biology|
Hi Magda -
Trying this with an animal would be very complicated. It would also require quite a bit of sophisticated equipment. Plus, if you fail, you have to realize that the animal dies! For these reasons I would recommend against doing such a science fair project.
However, people regularly freeze *bacterial* cells and bring them back to "life." Ask your science teacher if you can obtain a non-pathogenic (doesn't cause disease) strain of Escherichia coli (E. coli). Places such as Carolina Biological Supply sell strains and the media needed to grow them. If you have access to equipment such as incubators, bunsen burners, and the means to incoluate media for culturing you may be able to try some interesting things. Again, a good long talk with your science teacher would probably be in order..
When I freeze bugs in the lab, I add a solution of glycerol to the liquid media in which the bacteria grow. Adding a stock of glycerol so that it makes up 10% of your final solution usually suffices (i.e. 1ml 50% glycerol to 9ml of culture media). This mixture can then be frozen. After freezing you can collect some crystals from your frozen media, streak them onto a Petrie dish and see whether any colonies grow.
Media containing glycerol freezes at a lower temperature than water alone. If you want to study the effects of low temperature on the viability of cells, this shouldn't make a difference. However, if you specifically want to look at "freezing" you may need to find a freezer that goes to temperatures lower than regular freezers.
To do any experiments rigorously, you'll need to ask or find out how to do a dilution curve. It's not difficult, but you need to understand "powers of 10" and how to properly do the dilutions. An introductory text on microbiology should describe how to do it. Someone should probably help you with it as it involves some concepts that you probably haven't had in class yet.
Bacterial cultures often have ~1,000,000 cells, just in a milliliter! If you put 1mL of culture on a Petrie dish, the whole surface will grow bugs, and you won't be able to count anything! By diluting your starting culture, you reduce the number of bugs to a level that can be counted. The dilution curve accomplishes this
What can you do?
Hope this helps..
Lynn Bry, MadSci Admin
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