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Microbial Physiology notes lec8 10-11-10

Microbial Physiology notes lec8 10-11-10 - Microbial...

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Microbial Physiology Lecture 8: October 11, 2010 Cell Polarity continued 2. Protein Localization in Caulobacter a. The flagellum, pilli and Chemotaxis machinery are all made before septation ( cell division) a. The flagellum and pilli are located at the swarmer cell pole, and there are also certain proteins like MCPs ( the receptors for chemoreception) which are also located exclusively at swarmer cell pole and this occurs before pre-division so this is the pre-divisional cell that displays this polarity b. ½ of the pre-divisional cell generates the swarm cell, and the other ½ generates the stalked cell that has elements of adhesion b. there is a conserved domain near the C-termini of all MCPs( chemoreceptor) that is required for polar localization ( it recognizes che W and che A) a. E.coli has these conserved motifs as well MCPs are also located polarity, but in E.coli, you have them as a patch at both poles, while in Caulobacter you have them as a patch, but only at 1 pole, the swarm cell pole b. When it goes from the swarm cell to the stalk cell you rearrange the whole surface and therefore lose the supposed division scar, in which the division really occurred right where you’re generating the flagella and pilli c. The conserved C termi of all MCPs are known to be the binding sites for che W and che A and che W and A are the ones that determine the polar localization of MCPs i. C terminal domain on the MCPs that gives rise to polarity is in fact the same signal, that is recognition of che A and W— which is responsible for the polarity of the E.coli cell with respect to MCPs ii. BUT is caulobacter, the MCP is made exclusively at the swarmer pole, so there has to be something that gives rise to localized txn c. Caulobacer MCPs are made at the swarmer pole, degraded in transition, and made again strict temporal control a. Why in caulobacter do you have a patch of proteins only occurring at the swarm cell pole, rather than both poles as in E.coli? i. Because in caulobacter you don’t have 2 poles that are similar, because the stalk pole was from the previous cell division, not the most recent cell division has a completely different shape it was remodeled to form the stalk cell because when
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you have a cell division, you generate 1 stalk cell, and 1 motile swarm cell ii. The swarm cell undergoes differentiation back to a stalk cell, and the differentiation from swarm cell to stalk cell takes an extra 40 mins longer than it takes a stalk cell to undergo cell division during cell cycle it makes sense for the swarm cell to take longer because it has to do much more iii. The swarm cell is the small cell, frequently when bacteria divide, 1 of them is bigger than the other, and caulobacter has 2 cells, swarm cell is 40% total volume of the predivisional cell, and the stalk cell is 60% total volume of the predivisional cell We have asymmetric division, can tell by looking at the light microscope because it has distinct characteristics,
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Microbial Physiology notes lec8 10-11-10 - Microbial...

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