9/2 Chapter 3: Bacteria and Archaea (3.2 learning modules to Pili and Nanotubes)

What are the external structures of a prokaryotic cell from outside to inside?

1. Flagella

2. Fimbriae

3. Pili

4. Nanotubes/nanowires

5. S Layer

6. Glycocalyx

FROM OVERVIEW SLIDE: What is an S Layer? (Add to later slide)

• Single layer of a protein linked (only in few bacteria) together like tiny chain link fences

• Only produced when bacteria are in a hostile environment (outside/on top of cell wall)

FROM OVERVIEW SLIDE: What is an Glycocaylx? (Add to later slide)

• Coating of repeating polysaccharide or glycoprotein units (outside cell wall) (sugar protein)

• Can be a slime layer or capsule (one or the other but not both)

What are the differences between the slime layer and capsule of a glycocaylx?

1. Slime layer: loose (to bacteria cell wall), protects against loss of water and nutrients (like jelly that can absorb water)

2. Capsule: more tightly bound (to cell wall), denser, and thicker

• Important when dealing with pathogens (Immune cells can’t grab capsule as easily which is important for pathogens)

What are the external structures of a prokaryotic cell from outside to inside? (Describe Flagella)

Primary function is motility (movement can swim/move which helps it run from pathogens)

• The structure is three distinct parts:

1. Filament: (outmost part)

2. Hook (sheath): 360 degree connect anchor to filament

3. Basal body: Anchors in bacteria strongly

What is the arrangement of flagella? (What is polar arrangement and the subtypes? What is the non-polar arrangement called)

• Polar arrangement: flagella attached at one or both ends of the

cell (There are 3 types)

1. Monotrichous: single flagellum

2. Lophotrichous: small bunches or tufts of flagella emerging

from the same site (All from one point)

3. Amphitrichous: flagella at both poles of the cell

• Peritrichous arrangement: flagella are dispersed randomly over

the surface of the cell

What it’s important about the flagellar function: motility?

Chemotaxis (Chemical Movement): movement of bacteria in response to chemical signals:

• There is Positive vs Negative chemotaxis (Toward or Away)

• Ex: Toward nutrients or away from disinfectants

What are the two types of flagella function motility when it comes to Chemotaxis? Not positive and negative, but ______ and ______

1. Run: rotation of flagellum counterclockwise, resulting in a smooth linear direction (Distance traveled)

2. Tumble: reversal of the direction of the flagellum, causing the cell to stop and change course (Change direction)

• They don’t all run in 1 direction; They run in a zig-zag pattern

What are the external structures of a prokaryotic cell from outside to inside? (Describe Fimbriae)

• Small, bristle-like fibers sprouting off the surface of many bacterial cells (Shorter than flagella and present uniformly all over surface of bacteria in large numbers)

• Allow tight adhesion between fimbriae and epithelial cells, allowing bacteria to colonize and infect host tissues (ex: can attach membrane like UTT LISTEN TO LECTURE FOR THIS)

What are the external structures of a prokaryotic cell from outside to inside? (Describe Pilus/Pili)

• Used in conjugation between bacterial cells

• Well characterized in gram-negative bacteria

• Type IV pilus can transfer genetic material, act like fimbriae and assist in attachment, and act like flagella and make a bacterium motile

What are the #’s of pili compared to fimbriae?

They are present in large #’s but less than fimbriae and are short

• Helps with motility and attachment

What is Conjugation between bacteria?

Two bacteria form a bridge of pili that info can be passed between them

• Helpful for plasmid DNA and restance to antibodies

• Ex: One bacteria transfers plasmid making 2 resistant bacteria and on; it just grows in numbers