Lecture 6 Flashcards
Ways that bacteria can produce motility?
- Flagella
- Axial filament (spirochetes, internal flagella, flexes, bends, spins)
- Twitching: type IV pili at each end
- Gliding: slime production
- Brownian motion (not motility, hit by H20)
Under a microscope, non-motile bacteria often appear to shake. Why?
Brownian motion
What is chemotaxis?
Chemoreceptor (proteins in plasma membrane or periplasmic space) tells bacteria to move toward attractants and away from repellents.
List the four flagella arrangements studied in this class?
- Monotrichous/polar 1 flagellum
- Amphitricous, 1 flagellum at each pole
- Lophotrichous, tuft of flagella at one or both ends
- Peritrichous, flagella evenly spread over whole bacteria
Functions of bacterial capsule?
- Protect bacteria from drying out (contains H2O)
- Adhering to surfaces
- Evading host immune system by preventing phagocytosis
- May confer growth advantages
- Protects against bacterial viruses
- Protects against chemicals and detergents
What components are found outside the bacterial cell wall?
- Polysaccharide layers
- Biofilms
- Protein Layers
- Mycolic acid layer
- Pili and Fibriae
- Sex Pilus
- Flagella
What layers are found as polysaccharide layers (in to out)?
- Capsule - well organized, not easily removed
- Slime layer - less well organized, diffuse and easily removed
- Glycocalyx - sugar shell
What is a biofilm?
Protected by and attached to teeth, rocks, surfaces by layers of polysaccharide.
How does biofilm affect gene expression?
Quorum sensing can lead to increased or decreased gene expression
What is an S layer?
Patterned like floor tiles, helps give cell shape to protect against pH, osmotic pressure and anti-bacterial enzymes. Aids in virulence
What is the mycolic acid layer?
Acid-fast stain (+), resistant to dehydration, antibiotics and phagocytosis (ex. TB and leprosy)
What are pili and fimbriae?
Small, short hair like appendages (3-10 nm diameter) that help adhere to the host and type IV can twitch for mobility
What is a sex pilus?
Larger, hair like appendages (9-10 nm diameter) that is found with bacterias with plasmids with sex pili genes and transfer genetic material
What does chemoattraction assays test?
If the bacteria is chemotactic (has both motility and chemoreceptors), tests what is toxic to said bacteria.
What is flagellin?
The hollow tube of protein that makes up the majority of a flagellum.
