Science Buddies: "Ask an Expert"

Hi, i am in the seventh grade, and i am doing a project using E. coli bacteria. The culture i received was already growing on agar, so I have a couple questions:

1. The culture was growing on Tryptic soy agar, however I want to transfer the bacteria to my petri dishes prepared with nutrient agar. I am afraid that the transfer would not be successful, since the E. coli was previously growing on Trpytic soy agar, and I want to culture it on nutrient agar plates.

2. The slant tube said to store the E. coli at 4 degrees Celsius. I have stored it since yesterday afternoon, and today at 9:00 EST, I checked the temperature of my refrigerator (I stuck a thermometer in there) and it read 2 degrees Celsius... I am very worried that the 2 degrees may have made a difference.

Thank you

Hi Jessica, here the procedure on how to transfer your bacteria. http://delrio.dcccd.edu/MFarinha/lab_ma ... sfers.html As far as temperature is concern, the package insert should have information about the acceptable "temperature range", but in general a two degree different should not be significant.

Michael

Additionally, I would like to add that transferring your bacteria from tryptic soy to nutrient agar should not have too much of an effect (if any at all) to your culture but it is good that you're paying attention to such subtleties while doing your experiment!!
And I agree with the other expert that a two degree difference should also not have much of an effect but if you can get to that four degrees by adjusting your refrigerator somehow, then you definitely should!

Hope that helps!
Prasad

Thank you for your help. My experiment is almost done (I am giving the agar plates an extra day or two) and the E. coli seems to have grown despite the fact that it was subcultured on tryptic soy agar and then cultured, for my experiment, on nutrient agar.

Hi,

1. The transfer from TSA to nutrient agar should be fine. In my opinion, the subculture should have been growing on nutrient agar, not tryptic soy, but that all depends on where you purchased the bacterium.

2. 2 degrees will not make a difference. In my high school lab a couple yrs ago, we stored E. coli K-12 in a refrigerator, but then we later discovered that the refrigerator was at 14 degrees Celsius. Yet it still grew perfectly fine on our nutrient agar plates.

Good luck,
Jane C.