Measuring Bacteria

[Grant B.]

I am testing if UV light can kill bacteria on meat or fish. I need a way to show the amount of bacteria that is killed in the variable group (the meat or fish that receives the UV light). Is there anything that can show the amount of bacteria that has been killed? I have heard of a powder that can show bacteria. Is there a more effective way? If so, could you please tell me what it is and where I can purchase it. If there is not a more effective way than the powder, where can I purchase the powder? Thank you very much.

[donnahardy2]

Hi Grant,

In order to measure the effect of UV light on bacteria, you will need to culture (grow) them before and after exposure to UV light. Please look at the microbiology section of the science buddies website for information on safely growing bacteria for a science project:

https://www.sciencebuddies.org/science- ... o&from=TSW

Let us know if you have more questions.


Donna Hardy

[Grant B.]

Thank you for the reply. I looked in the microbiology section, but it was not relevant to my project because I will be using raw meat and there will already be naturally occurring bacteria on the meat. What I would like to know is if there is a way I could measure the naturally growing bacteria before and after the exposure to UV light. Is the powder I mentioned in my first email the most efficient way? Where can I purchase something that will show the bacteria on the meat? Please let me know as soon as possible. Thank you.

Hi Grant,

In order to measure the effect of UV light on bacteria, you will need to culture (grow) them before and after exposure to UV light. Please look at the microbiology section of the science buddies website for information on safely growing bacteria for a science project:

https://www.sciencebuddies.org/science- ... o&from=TSW

Let us know if you have more questions.


Donna Hardy

[MelissaB]

Grant,

I'm afraid I don't know of any powder like the one you're asking about, although I do know there is a pill you can chew up that will show bacteria (=plaque) on your teeth. You could try grinding up the pills, called 'disclosing tablets,' and putting the powder on the meat, but I don't think that would work because the bacteria on the meat will be different from the bacteria in your mouth and may not react to the powder. Still, you could try it and see. You can find websites that sell disclosing tablets using your favorite search engine if you want to do that.

What I think Donna was implying is that it might be easier if you took swabs from the meat before and after the UV light treatment (and from some other meat before and after an equal amount of time as a control), did a serial dilution on the bacteria on the swabs using agar plates, and then estimated the number of bacteria on the meat. Most, if not all, of the procedure for doing that is discussed in the microbiology section, but if you decide to go that route and need help please don't hesitate to ask.

Hope this helps!

[donnahardy2]

Hi Grant,

I do apologize for not providing more explanation before I referred you to the science buddies website. Melissa is right, the standard way to measure bacteria on meat is to take a culture using swabs or direct contact and grow the bacteria on agar plates. Bacteria only grow on the surface of meat, so you would need to just test the surface. Bacteria are only about 1-2 microns in size, so there's no easy way to measure them directly, and I've never heard of a powder to do this. For this project, you would need some nutrient agar, Petri dishes, sterile swabs, and a place with a constant temperature to incubate the plates. This type of experiment takes a few days to complete; you would probably need time to do a preliminary experiment to find out what kind of dilutions you would do to get measurable results. This would be an excellent project because you would get quantitative (measurable) results.

What are you trying to accomplish with your project? What is your purpose? Perhaps there's another type of experiment that would help answer your question.


Donna Hardy


Donna Hardy