chapter nine is on Gene transfer and genetic engineering this chapter is really about a lot of the cool things that bacteria can do there's not a lot of genetic diversity with bacteria remember they're not undergoing sexual reproduction they're undergoing asexual reproduction with binary fision so they're not combining genetic sources so they don't have the variability like we have with humans we talk about meiosis and introducing that genetic variability so that we're not clones of our parents and not clones of our siblings when bacteria divide they're going to be clones of each other so there's not a lot of genetic diversity so what's cool about this chapter is it talks about all of the ways that um bacteria can introduce different genes and kind of scramble the genes up and get some different uh recombinations and some genetic diversity so a little bit about Gene transfer in the last chapter we talked about vertical Gene transfer that's with heredity so passing DNA down to the Next Generation the only way that we can transfer our genetics is to our Offspring to the Next Generation bacteria can do the same thing they can actually undergo vertical Gene transfer so they can transfer their genes to to the Next Generation but procaryotic cells can do something that eukaryotic cells can't do they can undergo lateral or horizontal Gene transfer so two bacteria side by side uh side by side on a plate in a lab can actually exchange genetic material this is exchanging genetic material with somebody in the same generation this is not something that humans can do we can't stand next to somebody and suck up their DNA into our genome if that were true I'd probably stand next to Carrie Arnold all day long trying to get her smarts but bacteria can do this and in order to undergo lateral or horizontal Gene transfer it's going to be donated from one cell to the next so in this chapter we'll be talking about donors and recipients anytime that we are combining DNA this is what's called recombination so these bacteria basically become recombinants at the end of this chapter we're going to talk about how we can actually use that to our advantage so that we can use bacteria to make vaccines and to make medicines and things that we need the other cool thing that bacteria can do is that they can actually take DNA in from the environment and incorporate it into their genome this is what's called transformation again we cannot do this you can't put your hand on a tabletop that maybe has some DNA and have your body suck it up and put it into your genome however bacteria can do this and the first discovery of transformation that bacteria can actually take up fragments of DNA from their environment and the way that I remember transformation is taking up fragments transformation has an f and it fragments begins with f you know how I like those letter associations there was a scientist Frederick Griffith in 1928 that was actually working with um a couple of different strains of strep pneumonia and he discovered that there was a smooth Colony so a smooth strain that had a capsule and remember capsules are that really thick gly oalx and that made them pathogenic they were virulent they could actually cause disease why because first of all bacteria that have capsules they're really difficult to kill second of all if they have capsules they can stick to cells if they can stick to cells then they can cause damage to cells and that means they're dangerous the other strain that he was working with was another strain of strep pneumonia but this was a rough Colony it did not have a capsule so it didn't cause disease it was not virulent so he did a couple of experiments with these bacteria and what he did was he had some experiments where he injected the bacteria into mice so if you take a look at this picture up at the top so that little mouse on the far left this was actually inoculated with heat killed smooth bacteria remember that smooth bacteria had the capsule so it was virulent it was dangerous here's the thing though Griffith killed it he Zapped it with heat and that bacteria died so when he injected it he basically injected the mouse with dead bacteria and as he expected the mouse lived with another experiment he did not kill it so he had the live virulent smooth bacteria injected it and the poor little mousy died which he expected he knew that this bacteria was dangerous then he looked at the rough strain so he took that rough strain which was non virulent injected it in The Mouse and the mouse lived so what he did was he kind of combine the two experiments where the mice lived so he took the heat killed smooth bacteria with the capsule combined it with the safe rough bacteria without the capsule combined them and to his surprise the poor little mousy died so what was actually happening in the first experiments both of the mice lived why is it that this mouse died well what he found was that when that bacteria was heat killed it allowed the cell to lice and some of that DNA from that bacteria escaped and was in the environment that rough bacteria then took that DNA that had the codes to make the capsule Incorporated it into its genome and then was basically transformed into that smooth dangerous bacteria so this was the first evidence of transformation that bacteria could actually take fragments of DNA from their environment here's my little picture that I drew out and we've got on the left hand side this is our smooth dangerous bacteria looks kind of angry there and I tried to draw a little Capsule that's a bacteria that he zapped with heat so when that bacteria was zapped with heat it was killed and it liced and so some of the DNA was in the environment so here's are on the right side Our rough safe fluffy Cloud looking bacteria without a capsule it was able to take in that DNA so here that transforming substance is the DNA and now that safe bacteria was transformed to that dangerous the bacteria that had the smooth capsule because now it had the genes to make that capsule I kind of think of this as being like the hero is transformed into the villain in in our house we like to watch a lot of Marvel movies um and so we always see some strange things like that happening in Marvel movies so I think about the nice hero is then being transformed into the villain now not all bacteria can do this bacteria have to be competent meaning that they have to be able to open up take in that DNA and then close up and remain healthy so bacteria that are competent they actually have this competence factor and so this competence Factor these proteins allow them to open up take in that DNA and remain healthy not all bacteria are able to do this we could actually buy competent bacteria so we could go to a supply house and we could actually buy competent bacteria so that if we wanted to do some genetic experiments we know that this bacteria would be able to open up we would be able to put that DNA um into that bacteria and we could do some experiments so not all bacteria can do this only competent bacteria can do this so here's another little picture of transformation so here we've got the bacteria and you can see that it's got its circular chromosome and in its environment is fragments of DNA so this bacteria it's competent it can open up it can take in that DNA and then if you see in that third picture it can incorporate that DNA into its genome so it's becoming that recombinant recombination is happening so in that bottom picture you can see where this competent bacteria has acquired the genes A and B from the environment now if let's say that A and B help to code for a capsule or maybe um helps that bacteria be resistant to an antibiotic now that bacteria has acquired additional genes so this is how one way that bacteria can actually increase their genetic diversity