lecture 12: microbial cell walls Flashcards
(19 cards)
What is the purpose of a cell wall?
Protects the cell from osmotic pressure, preventing it from bursting.
Maintains cell shape.
Provides structural support.
How much pressure can cell walls hold back?
Up to 203 kPa (=car pressure)
What are the two carbohydrates that make up a bacterial cell wall?
N-acetylglucosamine (NAG)
N-acetylmuramic acid (NAM)
How do the sugars in cell walls connect across and up/down?
Horizontally (across chains): Linked by β-1,4 glycosidic bonds.
Vertically (up/down chains): Connected by peptide cross-links.
What types of bonds are needed for the cell wall?
Glycosidic bonds (between sugars)
Peptide bonds (between amino acids cross links)
Gram + vs. Gram -
How are their cell walls different?
Peptidoglycan Layer:
Gram + = thick
Gram - = thin
Gram + vs. Gram -
Who has what acid? LPS? Periplasmic space?
Gram +:
Teichoic Acid (stability and ion transport)
Gram - :
LPS (with Lipid A acting as the endotoxin)- outer
Periplasmic Space
What is in periplasmic space?
Located in the Gram - and contains digestive enzymes, protein pumps, and transport protiens.
Gram-negative bacteria have endotoxin (LPS) built into the cell wall – what is the actual endotoxin?
Lipid A, a toxic component of LPS.
Gram + and Gram -
Who has the interbridge in their cell wall?
Gram +
ex. staphylococcus aureus
interbridge: peptide cross-link (structural integrity)
Acid fast bacteria- what acid do they have? What does it prevent from working?
Contain mycolic acid (a waxy lipid).
Prevents dyes from penetrating, requiring acid-fast staining.
Example: Mycobacterium tuberculosis.
What are the Archaea cell walls made of?
Pseudomurein: Contains NAG, but no NAM.
S-layer: Made of proteins or glycoproteins, forming a paracrystalline structure.
Do Archaea cell walls have NAG? NAM? If not what do they have?
Have NAG, but lack NAM.
Instead of NAM, pseudomurein contains N-acetyltalosaminuronic acid.
What is Glycocalyx made out of?
sticky layer of carbohydrates and protens
What is the difference between the capsule and slime layer in glycocalyx?
Capsule:
Structure- thick, well organized
Attachment- firmly attached to cell
Function- protection from immune system
Slime Layer:
Structure- loose, unstructured
Attachment- easily washed off
Function- helps in adherence
What are Biofilms made out of?
Extracellular polymeric substance (EPS) (proteins, polysaccharides, and DNA).
Where might you find Biofilms?
Medical devices (catheters, implants)
Teeth (plaque)
Rocks in water bodies
What is the purpose of Biofilms (three things)?
- Attachment to surfaces or other cells
- Protection from antibiotics and immune attacks
- Communication via quorum sensing
