if you want plasmid dna from cultures of e coli why dont you do a simple procedure of total dna extraction?

Doing a full DNA extraction will produce contaminated plasmid DNA sample.

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Let me take you through an example.

I am sure you have heard about a DNA mini, midi, or maxi prep? correct?

All of the procedures are the same, but you have different volumes of bacteria cultures.

1.) pellet down bacteria culture

2.) lyse bacteria cells. (This releases the bacterial DNA (bDNA), plasmid DNA (pDNA), and other cell debris).

In your case, this is a total DNA extraction, BUT you want to separate the bDNA from the pDNA. Remember, you want the pDNA for experiments.

Now you will denature your DNA and collect the pDNA by column extraction and eventually ethanol or phenol precipitation.

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I do not know any other ways of getting pDNA from a bacterium cell. Within the first group of steps, you are taking the total DNA out of the cell, but you are then purifying the DNA to get your pDNA.

good luck.

i dunno.....honestly