Lect10-KR - Bacterial Appendages and Secretion Systems...

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Bacterial Appendages and Secretion Systems PMB/MCB 112 September 22, 2010
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Capsules Polysaccharide + protein Hydrophilic polymer Repels viruses Repels hydrophobic anti- microbial compounds Attaches to host tissues Protects against phagocytosis Protects against desiccation Participates in biofilm formation Capsules appear light because they exclude the stain.
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Caulobacter H. pylori E. coli Bacterial flagella Up to 10 μm long, filament is 14-20 nm wide Helical polymer of flagellin protein Enables cell to swim through liquid Anchored in cell membrane by a rotary motor Flagellar rotation acts like a boat propeller
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Tethered E. coli End of flagellum attached to slide using an antibody As flagellar motor turns, we see it as rotation of the cell body Motor is driven by proton gradient across the cytoplasmic membrane Howard Berg, Harvard 300 Hz maximal rate 1000 protons/revolution Cells can travel up to 60 cell lengths/sec
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MS ring-anchor in cytoplasmic membrane P ring-anchor in peptidoglycan L ring-anchor in outer membrane C ring-proteins associated with inner face of cytoplasmic membrane L P MS C
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MotA and MotB are the stator , because they DON’T rotate. Other proteins (like the rod, hook, and filament) are part of the rotor , because they DO rotate. MotB is bound to the peptidoglycan layer and MotA Protons pass through a channel in the MotA protein, causing conformational changes that PUSH on FliG, part of the rotor in the C-ring. FliM and FliN determine which direction the rotor turns when protons flow through MotA.
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The BASE is built from inside to outside, but flagellin monomers are added at the FAR END of the filament, under the cap The long axis of the flagellum is a channel through which protein components are secreted. Flagellin monomers travel through a 3 nm hole in the filament to the far end, where they are assembled under the cap. Flagella are lost by mechanical shearing.
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Lect10-KR - Bacterial Appendages and Secretion Systems...

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