Bacteria in Science Fair Projects
Country: United States
Date: December 2005
I am in the eighth grade. I want to to do a science fair
project on killng bacteria. My project is me trying to see if household
seasonings such as season salt can killed bacteria. I want to know how to
find out how much bacteria has been killed each day and how to run the
trials successfully? And one more thing, do you think this is a good idea?
I think these bacterial inhibition experiments are OK as long as they are
use an innocuous strain of *E. coli.* These strains can be obtained from the
ATCC (American Type Culture Collection) or from biological supply houses
like Carolina Biological Supply. Specifically, the seasoned salt experiment
would not reveal much because salt alone would inhibit virtually all
bacterial growth. Dropping a few grains of a seasoning on a plate seeded
with approximately 10^6 bacteria, should show a zone of inhibition around
the seasoning if it does inhibit growth.
Ron Baker, Ph.D.
I can think of a lot of reasons NOT to attempt such experiments:
2. Control setups (temperature,
3. Defined objective(s).
4. Equipment/measurement/experimental methods.
A particular school might have a staff member that can address these
(and other) issues, but that is the exception, not the rule. I don't think
you have to be a PhD in chemistry to recommend NOT doing experiments with
mercury, elemental phosphorous and any number of other chemical substances.
Any proposal for a science fair project should be able to provide definite
answers to the above reasons
before beginning any such project.
Vince Calder Ph.D.
I think that this is a great idea but I'm a little worried about you doing it
at home. It depends what type of bacteria you will be using. If you are
using bacteria you collected yourself, it could be dangerous because you
don't know exactly what you are working with. If you order it from a
biological supply company, order something like Bacillus megaterium that is
not known to make people sick. I also think you should work under the
guidance of a teacher because it is very easy to contaminate your work if
aren't super careful.
As far as the experiment is concerned, you should do
serial dilutions of your bacteria until you find a plate that has a number
bacteria you can count.
You can google "serial dilutions + bacteria" and
probably find directions how to do this, or look in any microbiology lab
manual. This way, you can actually count the bacteria and determine if the
concentration of your spice, etc. has an effect on them. I would also
familiarize myself with the rules of aseptic technique (you can also google
this) that will tell how to work with bacteria safely and also to keep from
contaminating your work with other bacteria.
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Update: June 2012