lecture04

lecture04 - 20.106J Systems Microbiology Lecture 4 Prof....

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20.106J – Systems Microbiology Lecture 4 Prof. Schauer ¾ Reading for today: Chapter 6 – On Growth ¾ Problem set due today ¾ Today: Growth – in microorganisms it’s different from in metazoans – increase in number of organisms instead of size o Binary fission o Other methods: ± Organisms that replicate their DNA many times over, than split into many parts at once ¾ Next week: metabolic regulation ± Binary Fission o Time from bacterium to bacteria is a generation o Generation time is how long it takes o 20 minutes is a rather fast generation time. 8 minutes is the world record. o We look for bacteria that can replicate fast, or that can replicate in extreme conditions. o Cell content replicates before division. ± Fts proteins and the “divisome” o FtsZ aligns before division o The most intense signal occurs at the center edges due to the 3- dimensional shape ± Peptidoglycan synthesis o Peptidoglycan needs to be extgended for the cell to grow o The balance needs to be right, so cell integrity isn’t compromised o Antibiotics bind to DNA binding proteins like FtsI, so that those enzymes aren’t available for the peptidoglycan synthesis, and the bacterium lyses. (Autolysins without autolysis) o The FtsZ ring leaves a scar in the cell wall, which you can see later ± Peptidoglycan structure o Two planes with cross-links in between. These cross-links give it its integrity o MreB allows a variety of shapes -- not just spheres ± Exponential Growth o Because bacteria undergo binary fission, they can replicate into mind- boggling numbers very fast (exponential rate) o After two days of unregulated growth one bacterium’s offspring would
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lecture04 - 20.106J Systems Microbiology Lecture 4 Prof....

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