Science Buddies: "Ask an Expert"

For my science fair project I am testing Salmonella on raw meat using PCR. I need to find a Salmonella positive control for my gel electrophoresis, where would I be able to purchase just a positive control (without the kits)?

Hi there!

This sounds like an interesting experiment. Have you checked out Carolina Biologics? They sell a lot of great science things for school projects! I went on their site and did a search for salmonella and came up with a few hits. I think this should be helpful for you! http://www.carolina.com/browse/product- ... ubmit=true


Good luck and let us know if you have additional questions!
Nikki

Hi,

You can buy cultures of Salmonella enteriditis or S typhymurium from Carolina Bio as Nikki suggested, just be aware that these are human pathogens and can only be sold to a college or university. Also, the bacteria need to be handled under biosafety level 2 conditions--personal protective clothing and a laminar flow biosafety cabinet.

But really, all you need for a positive PCR control is purified Salmonella DNA. Maybe if you call Carolina Bio and talk to tech support they might be able to help you with this.

Good luck!

Sybee

Thank you both for the feedback! If I do decide to purchase a vial of Salmonella and then heat it in a boiling water bath to exploit the bacteria and obtain only the DNA, would I be able to use that as my positive control?

Just boiling is not the best way to isolate DNA for PCR. Heat can disrupt the cells, but you still have a mixture of proteins, lipids and RNA along with the DNA and this can mess up your PCR reaction. There are simple methods for cell lysis, DNA extraction and purification but they require enzymes and toxic chemicals that you wouldn't be able to use in a high school lab.

Carolina Bio sells a non-toxic DNA extraction kit that can be used for E coli but I'm not sure if it will work for Salmonella:

http://www.carolina.com/dna-extraction- ... ?question=

You can call the company and ask them if the kit will work for Gram-positive bacteria like Salmonella. I think it would work well enough to provide you with some control DNA--certainly better than just boiling.

How did you plan to remove bacteria from the meat and isolate the DNA? You probably should use the kit to isolate DNA if you were just planning on boiling a part oft he meat and doing PCR on it.

I hope this helps. Ask more questions and we'll try to get you on the right track to succeed with this project.

Good luck!

Sybee