Science Buddies: "Ask an Expert"

How much does a 4 inch petri dish weigh with 1.2 grams of agar solution in it? Also, how do you measure the amount of bacteria grown in a petri dish without opening the dish?

thanks so much!

How much does a 4 inch petri dish weigh, in grams, with 1.2 grams of agar solution added to it? Also, how do you measure the amount of bacteria in a petri dish with out opening it?

Thanks so much!

Hi,

Welcome to science buddies! You have posted your question in the math and computer forum, so hopefully a moderator will move it to the life science section so the other biologists will see your inquiry.

It sounds like your project is completed and you need to quantitate the growth of bacteria on the plate to include in your results section without opening it. If you have grown unknown bacteria on your plates, it's definitely a good idea not to open the plates. To use weight to measure the amount of growth, you would need to weigh a Petri dish with the agar before you inoculated the plate. Do you have any unused plates available to weigh? That would give an estimate of the "before" weight. If not, then you could estimate the percentage of the surface of the agar that is covered with bacterial growth. If that is not appropriate for your project, then either take photographs and include a detailed qualitative description of the growth, or make a drawing of each plate and include the description.

Here is information from the science buddies website that gives information on the terminology that is used to describe bacterial colony morphology:

http://sciencebuddies.com/science-fair- ... ates.shtml

If you need more information, please let us know a little more about your project and why you are asking this question.

Donna Hardy

Hi lmcgarrell,

Re the weight part of your question:
I don't understand -
can't you just weigh the petri dishes?

Hi,

I have moved your topics to the proper forum and merged them so the experts can better help you. Please keep future posts about this project in this topic.