lecture notes

September 11, 2009

VI.
a. Twitching motility: jerky motion of bacteria w/pili along surface; pili attach to surface, retract
a. Flagellar motility: swimming smoothly through liquid
i. flagella analogous to motor on submarine
b. flagellar arrangement
a. polar: flagellum at one (or both) ends of bacterium, not all over:
i.
b. Peritrichous: flagella all over
c. Bacterial flagella are NOT the same as eukaryotic flagella!!!
d. Bacterial flagella are:
a. Rigid: act like propellers /motors to move bacterial cells
b. Made of flagellin: this protein forms filament that acts as propeller
c. Flagellin filament attached to “motor” made various integral membrane proteins.
i. “motor”= basal body
d. How they’re made to move
i. ATP→ADP and Pi (inorganic phosphate)—this provides energy for export of flagellin proteins through hook
e. How they move
i. Proton pump: H+ are pumped across plasma membrane of bacteria. The protons are trapped b/t cell wall and plasma membrane b/c H+ are charged (and membrane has hydrophobic parts)
1. Can’t diffuse because they are charged—only uncharged molecules can move across the membrane
ii. Protons can fall across gate in flagellar basal body—this spins the basal body spinning the flagellum
e. Eukaryotic flagella/cilia
a. Flexible: move like snakes
b. Made of tubulin and dynein: interaction btw these 2 proteins and snake like motion of eukaryotic flagella

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