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blotter paper or incubate?

Postby mom-to-ariana » Sat Apr 13, 2013 11:47 am

My First grade daughter is doing her first science fair project on hand sanitizer verses soap: which will kill more germs on hands? We purchased a kit that includes petri dishes, agar, swabs and blotter paper knowing that we would need to observe the germs. As we try to figure out exactly how to follow the scientific process we are running into a few hurdles. I am finding that many people will swab hands for bacteria, put it in the agar in the dish, wash hands with each product and place hands in agar again. I am unsure of what would be safe and consisitent as a bactria on her hands to grow? and how do they incubate the germs (does this mean just set in a dry, dark place for a period of time). The set we have has you place dirty hands in agar, grow bacteria, and soap/ sanitizer to blotter paper and whatch what happens in petri dish over hands. So we need to know:
What is best way to get a consisitent bacteria on hands (we are thinking a soil manure mix)?
Which way would be best to find results? Incubate bacteria after cleaning hands or use the blotter paper with cleaning products?
How do you incubate? Do you just set in dark place?
How do you count colonies of bacteria??
I am probably thinking about this too much, but I am not a "science person", although I am trying!

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Re: blotter paper or incubate?

Postby donnahardy2 » Sun Apr 21, 2013 8:00 am

Hi Mom,

Welcome to Science Buddies! This is a challenging project for a first grader. Your questions are very good and it's good that you asked them in advance. .

Here is a description of a project that is similar to your daughter's. The student tested the effectiveness of different hand sanitizers and soap and water after his hands had been coated with a consistent amount of bacteria. He pressed three fingers in agar, using a consistent technique, before and after cleaning his hands. This procedure should give consistent results and seems suitable for your daughter's project. ... lAkins.pdf

Here is a project idea that includes background information that would be helpful to share with your daughter. This project also includes safety information for handling agar plates after they have been incubated. ... p007.shtml

You will incubate the plates by sealing them with tape and turning them upside down to avoid condensation of moisture on the surface of the agar. Inclubate the plates at room temperature about 70 degrees F or 20-22 degrees Centigrade. Make sure you seal the plates and do not open them after the bacterial colonies have grown. Observe and make notes on the appearance of the plates every day for several days.

Garden soil would be a good source of bacteria, but I would not recommend using manure or any other source of bacteria from animals to avoid exposure to potentially pathogenic bacteria.

Please post again in this topic if you have any other questions.

Donna Hardy

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