How do you calculate the number of bacteria colonies?

Subject: How do you calculate the number of bacteria colonies?

Date: Sat Sep 5 16:57:42 2009
Posted by No name entered.
Grade level: 7-9 School: No school entered.
City: No city entered. State/Province: No state entered. Country: No country entered.
Area of science: Microbiology
ID: 1252195062.Mi

Message:


I have been working on my science fair project. My Science Fair Question 
is "What Disinfectant is Most Effective Against Bacteria?" I used isopropyl 
alcohol, Germ-X(62% Ethyl Alcohol), and anti-bacterial soap. When I am done 
with growing the bacteria I need to calculate the number of Bacteria Colonies 
that survived. I am using Lactobacillus. The bacteria found in Yogurt and 
other Dairy products. I will put in 25 ml of the bacteria and the disinfectant 
with it. I will place the solution in a petri dish with agar. Then place it in 
an incubator at 34 degrees Celsius. I then will let it grow for 72 hours(3 
days). I need to calculate the number of bacteria colonies. Is there a formula 
I can use. I have a microscope. I don't have enough time to count all of the 
colonies.

Thank You!!!

Re: How do you calculate the number of bacteria colonies?

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