Microbiology Lecture Notes September 25

September 23, 2009
2. Motility: flagella and pili
a. Pili
i. Example: adhesions on ends of pilli:
1. Are retractable extensions from bacterial cell envelope
2. Attach to surfaces and retract
3. Use peripheral membrane proteins to attach to surfaces
ii. Twitching motility
1. Jerking motion of bacteria with pili along surface; pili attach to surface, retract
2. Stick to a surface and retract
b. Flagella (NOTe: bacterial flagella are NOT THE SAME as eukaryotic flagella)
i. Bacteria swim more smoothly through a liquid such as water
ii. Flagella act like a motor for the bacteria that have them
iii. Analogous to motor submarine
iv. Flagella on sperm/eukaryotic organisms (NOT THE SAME!!!)
1. Eukaryotic are really just cilia
2. They are much smaller on bacteria
v. Flagellar arrangements
1. Polar (ex. P aeruginosa)
a. Means the bacteria have flagella located on one end or the other or both ends; they flagella are NOT all over the bacterial cell

2. Pertirchous (ex. E. Coli)
a. “Covered in hair”
b. Have flagella all over
vi. Eukaryotic cell flagella are just glorified cilia and are flexible
a. Flexible; move like snakes
b. Made of
i. Microtubules (tubulin) and dynein
ii. Two separate proteins and completely different than bacterial flagella
iii. Accounts for snaky motion of the flagella of the eukaryotic cell
vii. Bacterial flagella are:
1. Rigid: act like propellers w/motors to move bacterial cells
2. Consequence of the proteins they are made out of
3. Smaller than eukaryotic
viii. Flagellin
1. Protein that makes flagella rigid
2. Particles come together to make a long flagellan filament that acts as propeller
3. Makes the propeller part of the flagellin of the flagella
ix. Basal body and hook
1. Flagellan filament attached to “motor”
2. Made of various integral membrane proteins
3. Whole set of integral proteins is the basal body or “motor”
4. “motor” = basal body
5. Basal body of gram positive bacteria
a. no outer membrane
x. Use of ATP
1. Energy currency of the cell
2. Basal body breaks down ATP into ADP into phosphate to turn the motor
3. Why do bacteria not have mitochondria?
a. Fuels the transport of the flagellar protein filaments to go through the hook and out to make the flagella; polymerize together to make the flagella
i. Energy for this is breaking ATP into ADP
b. Proton pump system spins the flagellar motor
xi. How bacterial flagella are made:
1. ATP is broken down into ADP + P (inorganic phosphate)  this provides the energy to export the flagellan filament molecules out the hook through the basal body where they polymerize spontaneously into the flagella
xii. How they move:
1. Does not use ATP
2. Uses a proton pump system
a. H+ that have lost they’re electrons
b. H+ are pumped across the plasma membrane of bacteria
i. Proteins must be pumped across the plasma membrane because the inner part of the membrane is hydrophobic and only uncharged particles can move across a hydrophobic barrier or lipid membrane
ii. If protons were pumped across the plasma membrane and get into the cell wall; they cannot come back on their own; must be pumped
iii. Protons are trapped between the cell wall and plasma membrane b/c H+ cannot cross either of the hydrophobic layers of plasma membrane
iv. Protons fall through/across gate in flagellar basal body this spins the basal body which spins the flagellum like a water wheel when water falls down a water wheel
v. Energy gets taken from electrons coming out of the electron transport change; passing electrons down the electron transport change
xiii. Similarity to type 3 secretion systems
1. Bacterial flagella are very similar to secretion systems used by bacteria
2. These secretion systems are used to pump proteins out of the bacterial cell into the surrounding environment in particular by many pathogenic bacteria to inject toxins that kill eukaryotic cells directly into the eukaryotic cell
a. EX) virulence factors (any protein used by pathogenic “disease causing” microbes that contribute to disease in a particular host): pump directly into host cells thru type 3 secretion systems by some pathogenic bacteria
xiv. Similarity to ATP synthase of eukaryotic mitochondria
1. A brief digression on mitochondria and what bacteria do not have them

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