Microbial Physiology notes lec7 10-8-10

Bacteria knows they want to go in a different

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bacteria knows they want to go in a different direction -suppose bacteria is going up the concentration gradient of a repellent bad, so want to know when its time to switch, so that’s what this mechanism is for -but if you’re going up a concentration gradient of an attractant, something that is good for you, then you want to keep going up to it -they don’t respond to a spatial gradient but to a temporal gradient, so they swim a little while, and sense the [ ] and then stop and sense it again, and recognize that the [ ] is higher than it was before so they are going to keep going in the same direction, but if they sense that the [ ] is getting lower and its an attractant then they want to switch directions and go the other way, and so they reverse their swimming direction E. Cell division control in E. coli by MinCDE : 1. MinC: a FtsZ polymerization inhibitor its an inhibitor of cell division by inhibiting FtsZ prevents FtsZ polymerization and from binding of it at the quarters of the cell -FtsZ is a tubulin like proteins that forms a ring that contracts to give rise to 2 cells from 1 cell - Min= mini cell because in the absence of any of these proteins they form tiny cells by dividing in the wrong place, instead of in the middle - MinD: An ATPase that interacts w/ C and E, and stimulates Min C/D release from the membrane - MinD binds to C and forms a complex MinD has ATPase activity, and if you stimulate this MinCD will dissociate from its binding site and move wherever else there is a binding site in the cell - MinE : a topological specificity determinant stimulates MinD ATPase activity -MinE resides in the middle of the cell, but MinCD complex cant go to the middle because its already occupied, by MinE, so the MinCD complex moves over to the ¼ point where you want to prevent FtsZ -MinCD [ ] are relatively high at the ¼ points but not high at the ½ points, and therefore get cell division in the middle -there is tight regulation on the cell division 2. Min C/D shuttle between the 2 poles together while MinE shuttles between a pole and the median 3. MinCD prevents septation at the poles
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D. Caulobacter : Asymmetry is part of the cell cycle; it occurs in the pre-divisional cell and is a pre-requisite for cell division -before it divides it has 2 different poles and different functionality at those 2 poles -caulobacter is a stalked cell it has a stalk at one end of the cell to anchor itself in a highly nutritious environment -every time the cell divides, it produces a swarm cell and a stalked cell stalked cell stays at its original site, while the swarm cell is able to swim around and it looks for a new site to anchor
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  • Fall '10
  • Saier
  • DNA, swarm cell

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