The Bacterial cell Flashcards
What are drug (antibiotic) targets in bacteria?
Cell wall (PG, gram neg. OM)
Ribosomes (70S)
What is the composition of the gram negative cell wall?
Capsule
OM
PG
Periplasm
IM
What is the composition of gram positive cell wall?
Capsule
PG
Periplasm
IM
Name components of inner membrane
Phospholipid bilayer
Membrane proteins
Name functions of inner membrane
Permeability barrier
Transport solutes
Location of enzyme systems
Name bacterial lipids
Phosphatidylglycerol
Diphosphatidylglycerol
Phosphatidylethanolamine
Describe the periplasmic space
Aqueous
Densely packed with proteins
Sequesters potentially harmful enzymes
What are the differences between G. neg and G. pos cell walls?
G. neg
- thin
G. pos
- thick
- - techoic aicds
What does the cell wall prevent?
Prevents osmotic lysis
What does the gram negative OM doe?
Anchor for adhesin proteins
Prevents bile salts, antibiotics and lysozymes
Describe lipopolysaccharides (LPS)
Composed of O-antigen (variable chain of sugars)
Aids in immune evasion and forms selective permeability barrier
True or false: Low stimulation to innate immune system when LPS is detected
False: Highly stimulatory to our innate immune system
Explain PAMP
Molecule immune systems to see and react to pathogen
Overstimulation of immune system
What is PAMP?
Pathogen-associated molecular pattern (PAMP)
Explain endotoxin
Released via OM vesicles or cell lysis
Activator of macrophages, cytokines, inflammatory reponse
What are porins?
Transmembrane proteins that form a H2O-filled pore
Passive diffusion
What do lysozymes and antibiotics attack?
PG cell wall
Major target for antibiotics (Penicillin)
What are the glycan (carbohydrates) of the PG made from?
N-acetylglucosamine + N-acetylmuramic acid
How many amino acids constitute the PG peptide chain?
5 - tetrapeptide
Explain the PG biosynthesis
NAM-NAG subunits are transported across membrane which are assembled and crosslinked
What assembled the NAM-NAG chain?
Transglycosylase with glycosidic bonds
What cross links peptide sidechains?
Transpeptidase enzyme
What do Penicillin binding proteins do?
Catalyse transglycosylation and transpeptidation
True or false: PBS are targets for alpha lactam antibiotics
False: targets for beta-lactam antibiotics
Explain techoic acids
Found in g. positive
Lysis and release into blood stream
Rigidity
Is a bacterial capsule a pathogenicity factor?
Yes because not all bacteria have capsule which aids in immune evasion
How does the capsule aid in immune evasion?
Prevent phagocytosis
Explain how the bacterial ribosome is a drug target
Antibiotics disrupt protein synthesis
Tetracyclines bind to 30S synthesis
Macrolides block exit tunnel of ribosome
Explain mobile genetic elements
Carries genes (AMR)
What is bacterial conjugation?
Process by which genetic material is transferred from one bacteria to another
Explain narrow host range and broad host range plasmids
NHR: only replicate in certain species
BHR: replicate in many species
Explain bacterial metabolism
Bacterias can metabolise various sugars
Ability to utiilise different sugars (lactose, sorbitol)
Used for diagnostic purpose (MacConkey agar)
What do proteases do?
Degrade proteins in ECM which contribute to bacterial virulence
How are proteins secreted in bacteria?
SEC (general secretion) pathway
- if g. positive then job done
Translocation across g. neg IM
