Transformation in Bacteria

Hi everyone, and welcome to Biology Professor. Today, I want to talk about genetic recombination in bacteria. Bacterial cells are pretty cool because they have the ability to take up foreign DNA and actually incorporate it into their own genetic profile in order to make the protein that foreign DNA encoded for. This can give bacterial cells extra functionality, for example, they might gain new DNA that codes for toxins, that codes for virulence factors, that codes for antibiotic resistance, and the bacterial cell can actually gain new functionality through this way. There are three different mechanisms by which bacteria can obtain foreign DNA. These are transformation, conjugation, and transduction. I have videos on all three of these mechanisms, but today, let's talk about first one: transformation. Transformation is when a bacterial cell takes up foreign DNA from its environment by bringing that DNA from its extracellular environment across its plasma membrane. The ability of the cell to take up DNA across its plasma membrane in this way is called competence. Many types of bacteria are naturally competent and they can do this process with ease. Examples of such bacteria include species of Bacillus, species of Staphylococcus, and species of Streptococcus, and of course there are well-known human pathogens within each of these types of bacteria. So now let's look at this mechanism in a little more detail. Here we have our recipient bacterial cell. This here is its chromosomal DNA. So this is the DNA that it has had since it was produced by replication of previous bacterial cells. But there might be foreign DNA in this cell's environment. I'm going to draw this foreign DNA in red. This is DNA that is just going to be floating through the cell's environment. It might, for example, be from a previous bacterial cell that died and lysed, and pieces of its of this donor cell's DNA are now just floating around the environment. The recipient bacterial cell can actually take this DNA across its plasma membrane so that now this DNA is inside the cell, then through the process of recombination, the bacterial cell has its chromosomal DNA that has recombined with this foreign DNA so the foreign DNA has now been integrated into the chromosome. There might be some additional foreign DNA that was not integrated and it's just going to be broken down. Also, the bacterial DNA that was replaced by this foreign DNA is also going to be broken down and now we have this genetically transformed bacterial cell. This new DNA that's taken up can give it different functions, for example there are species of E. coli that actually produce Shiga toxin. This is a toxin that they obtained from the bacteria Shigella, so Shigella produces shiga toxin, some E. coli cells can produce it too because they're able to go through this genetic recombination process. This DNA could also encode for virulence factors, for example one virulence factor might be a capsule. If the bacteria can produce a capsule covering its outer cell wall, this may enable it to hide from a host immune system, and so this is why the process of transformation is very important to bacterial cells in that it can enable them to survive in different environments they might not have been able to otherwise.

Channel: Biology Professor

Views: 169,480

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Keywords: AP Biology, Transformation, Streptococcus, Competence, biology, Mcat, Staphylococcus, Biology Professor, biology 101, MCAT Review, Bacillus, DNA Recombination, Mcat Review, Mcat Biology, MCAT Biology, Frederick Griffith, HGT, horizontal gene transfer

Id: dKD19cXkWBw

Length: 5min 22sec (322 seconds)

Published: Tue Feb 04 2014