Question: How do you clone bacteria and what do you use to clone them?

Benjamin Hall answered on 14 Jun 2013:

I don’t clone the bacteria, as such.

I use the bacteria to clone certain genes I’m interested in.

A really brief overview of how you do it:

1. Take the gene you’re interested in and a piece of circular DNA called a plasmid (these exist naturally in bacteria). Cut open the plasmid, stick your gene in and then tie it all back together.

2. Take a small amount of the plasmid containing your gene, and mix it with some bacterial cells. Leave this on ice for twenty minutes.

3. Now we need to do something called ‘heat shocking’ the cells. E. coli (one of the bacteria I use) grow best at 36-37 degrees (body temperature). Heat shocking them at 42 degrees forces them to suck the plasmid up through their cell membrane.

4. Let the cells recover. To do this I add some liquid that’s really rich in all the nutrients bacteria need to grow and leave them at 36-37 degrees for an hour.

5. I then spread the liquid onto plates containing the nutrients bacteria need to grow. I leaves them overnight at 36-37 degrees and in the morning, all of the cells that contain my gene will have formed colonies on the plate. All the cells that didn’t take up my gene will have died. The reason this happens is because the plasmid makes the bacteria resistant to an antibiotic. If I add that antibiotic to the plate, the cells that don’t have my gene will be killed.

There are other ways of getting the plasmid into the bacteria. For example, when I want to do this with Agrobacterium (the species I use to transfer genes to plants) I actually give the cells a small electric shock.