why is a bacterium the best choice for genetic transformation?

Answer 1

None of the previous answers addresses what your actual question appears to be: Why is bacterium the best choice to create a transgenic organism?
The answer is because the moment a bacterium takes up the foreign DNA that you put into them they will be a transgenic organism. a transgenic organism is defined as an organism in which every cell has received the transgenic DNA. All you have to do in the case of bacteria is to mix them with the DNA, heat shock them and then spread them on Agar. Since bacteria only consist of a single cell they will become a transgenic organism immediately the moment they take up the DNA.

It is much harder to create a transgenic organism if the organism is multicellular. Imagine a human being consists of about 200 Trillion cells. you cant simply bathe them in DNA to get it into all of these cells. Mice which are a model to study human genetics and diseases are made transgenic by injecting the DNA into the prenucleus of a fertilized oocyte. This oocyte is then implanted into the uterus of a pseudo pregnant mouse which later gives birth to the transgenic mouse. This mouse still has to be crossed to generate more offspring that can then be studied.
The bottom line is its way more expensive and time consuming to generate transgenic higher organisms than bacteria.

Answer 2

1. Natural proclivities: It's easier to get them to take up foreign DNA, accept it, and stably express it than it is with eukaryotic cells, and particularly multicellular organisms as the person above pointed out. Also, bacteria commonly have naturally occurring independently replicating plasmids, elements of which can be used to construct useful plasmids to transform into bacteria to make them do our bidding.

2. Ease of growth: They're tiny and (often) quick and easy to grow. You can easily throw billions of them into your transformation reaction. Then if you successfully transform even one, you can have billions of copies of it in short order.

3. Ease of storage: Once you transform them and confirm that you've got it right, sometimes you want to freeze them down and save some for later. E-coli can be frozen in medium with 12% glycerol in a -80 freezer and you can just scrape off a little bit of the ice and put it in fresh medium and grow up billions of clones the next day. I've frozen mammalian cells down before and it was a lot more of a pain; they have to go in liquid nitrogen and they take quite a while to get going again after thawing.

4. Ethics: If something could be done in bacteria and produce the result you want, there's no good reason to use higher life forms. We always try to use the least sentient life forms possible in experiments and bacteria are right down there at the bottom of the totem pole of sentience as far as we know. They are presumed not to experience suffering the way a mouse could.

Answer 3

1. They reproduce rapidly- population doubles every 20 min or so for some bugs.
2. Availability of seveal selection markers (blue/white, drug resistance, etc).
3. Easy to grow, rarely require special supplements.
4. Recombinant proteins typically are similar to human proteins, though there can be differences in post translational modificantions.

Answer 4

Because they constantly evolve. Transporter proteins of D-alanine, needed to carry D-alanine to sites of cell wall repair, mutate into penicillin-binding proteins when challenged by penicillin. There are many copies of the D-alanine transporter gebne in bacterial genomes, and these genes mutate under selective pressure to PCB's.