Heat shock vs eletroporation - (Sep/06/2015 )

Hey guys i was just looking for some insight as to why some choose heat shock vs electroporation. More so in terms of quality of cell transformation, rather than price, because currently my lab is using an electroporator but have had some mixed results and was considering trying heat shock as an alternative.

Electroporation can give you much higher transformation rates, however, with good competent cells, I have found heat shock to be in the range of 10^8 - 10^9 cfu/ug DNA, which is about the same as typical electroporation rates. I have found that this varies with experience in preparing competent cells and the protocol used (I use the top10 one from openwetware.org on DH5a cells)

On the other hand, electroporation is supposed to be able to deliver 10-20 times the amount compared to heat shock, but in my hands never seems to do so.

To add to Bob's comments, chemically competent cells are also easier to make...requires less culture, and the cells only need a 1-2 washes whereas electrocomepetent cells require a greater volume of culture and 3-4 washes. 

As bob said the main advantage to electrocompetent cells is that they are typically more efficient. The only time I've ever absolutely needed the enhanced efficiency was to transform three plasmids at once. Chemical cells are good enough for double transformations, but not triple in my hands.

And you said price was not an issue...but $$$ is always important. Electroporation cuvettes can be pricey (2-3$ each). Chemical transformations require nothing extra. For the occasional transformation it's a non-issue but our lab does thousands of transformations each year so it would add up.

Thanks guys, yea we are just having some issues with cell expression in our lab and we only transform via electroporation and was considering using other protocols. My PI is very big into electroporation for only a single plasmid and she recently bought a new batch of cuvettes for the lab since we were having with transformations. I try a few transformations with either chemical or heat shock to see if maybe we have a better efficiency. 

Concerning you expression issues...are you freezing your expressing strains?

No we only do a single use on each strain grown. We will freeze only our competent cells at the moment, expression hasnt been the biggest problem for our lab as of late!

Cool. Yeah I've run into too many issues getting strains to express again after being frozen. Fresh transformations every time really is worth it. Good luck.