Microbiology Day 17 - Microbiology Day 17 March 19th DNA...

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Microbiology Day 17 – March 19 th DNA Exchange Slide 13 Lambda is often used a lot. It has the genome in its head and the protein head is a covering and its in one package. The genome is inserted through and into the bacteria. SO it binds to a receptor and infects a certain gene. Eukaryotic cells are different and they get in by endocytosis and membrane fusion. Slide 14 Phage therapy is being looked at where they use phage to kill pathogenic bacteria. Hopefully, the phage will attack the bacteria and not the host. We have these EM map and they use the phage enzyme to get rid of bacillus cereus. After enzyme treatment, there’s more cells lyzed. So d shows that lyzin is punching a hole in. There’s different ways of manufacturing phage to work. One way is to manufacture phage so that it infects the bacteria once and doesn’t make new phage, so loses ability to infect. So they are engineered so they don’t infect host. It’s like bacteria that eats oil reserves, so there has to be some genetic engineering to prevent it from spreading to environment Slide 15 Temperate phage is it can be lytic or lysogenic. The genome of virus can insert in the genome of the bacteria and as a result, there’s no new phage until it gets induced to excise out (lysogenic). Once this happens, it becomes an independent piece of DNA, it will start to transcribe and translate. In this case, the virus binds to a specific receptor and can take different pathways. The pathway it takes depends on its genetic and how quickly each genes are made. So lytic pathway starts making its coat protein and other proteins, and then leaves. It also alters the host’s genetic expression as well. That means that it turns off certain genes and turns on some. That’s why some viruses are associated with some cancers. It requires enzymatic action to inhibit excision. There’s an enzyme that blocks that enzyme that cut. What’s noteworthy is that after lysogeny and it excises, in rare cases, it can take some DNA out with it and bring host chromosome with it, and perhaps lose some of its own. So some viral DNA might stay in but when virus pops out take some of the host chromosome by random chance. There’s usually packaging maximum, so head that has the genome will only accept a certain amount of genome. So that limits how much host DNA can be transferred from one cell to another. Often that virus will lose infectivity because it can only accept a certain size which is the size of its regular genome and is missing some of the stuff it needs.
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