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a question on Death Rays: What Duration of Ultraviolet Exposure Kills Bacteria?

Posted: Wed Jan 23, 2019 8:51 pm
by vivinae
I'm here regarding the materials of this experiment (Death Rays: What Duration of Ultraviolet Exposure Kills Bacteria?). I’m wondering if we aren’t able to get an incubator for the Petri dishes, what can we use instead to heat it up?
Plz help:) thank you. Hi also adding on, how do you make the nutrient agar plates with the e.coli on top. Like what are the procedures to do so. Do we just make the nutrient agar and put it on the plate then after we just add the e.coli on top? One last question does the e.coli have to be freeze-dried or can it be a live culture? Please reply back asap thank you

Re: a question on Death Rays: What Duration of Ultraviolet Exposure Kills Bacteria?

Posted: Wed Jan 23, 2019 10:07 pm
by 17eugenekim
If you don't have an incubator, don't worry - an easy alternative is just to put the plates in whatever place you can keep consistently warm. If there's any place like that in your house, putting them all in a box there can work. Of course, I understand it's winter now - so you can also put in a heat lamp in the box that you can keep turned on, or if you can't get one, maybe just a light bulb would work too. Just make sure it's not anywhere near flammable objects.

The E.coli plating is done through a process called "bacterial streaking." Take a sterile cotton swab (sterile can mean that it is packaged one by one and you just opened the package, like a band-aid) and spread the E.coli around the plate. Let it dry before continuing. Our procedure suggests you change cotton swabs every three plates, to avoid cross-contamination.

I don't know where you are getting live culture from, but just make sure that 1) it doesn't contaminate anything else and 2) nothing else contaminates it. Basically, always use fresh gloves and other protective equipment, and always be careful when handling it. If you are careful, I don't think it should be a problem.

Hope that helps!