Listeria monocytogenes Flashcards
(9 cards)
Describe the attributes of L. monocytogenes that allow it to survive in food
Motile at 25°C
Psychrophilic (grows between 1-45°C)
Acid tolerant (pH between 4.3-9.6)
Salt tolerant (up to 10% w/v NaCl)
How is listeria transmitted, who is at highest risk, and how have outbreaks lead to food recalls in Canada?
- Commonly transmitted through contaminated food
- Risk factors - pregnancy, newborn, weakened immunity
- Responsible for deadliest foodborne outbreak in canada - 22 deaths
What is the life cycle of listeria monocytogenes?
six steps
- Adheres to surface of epithelial cells via the interactions of the surface proteins InIA and InIB with E-cadherin and the Met receptor
- Engulfed in phagocytic vacuole
- Lyses vacuolar membrane using toxin LLO
- Uses protein ActA to harness actin polymerization machinery and facilitates its intracellular movement via formation of comet tails
- Explots actin based motility for direct cell-to-cell spread to allow the dissemination of the infection to neighbouring cells via formation of plasma membrane protrusions
- Confined in double-membrane vacuole from which it escapes to restart it’s life cycle
What is LLO?
Pore forming cholesterol cytolysin (CDC) - facilitates escape from phagosome, active at pH 5.5 (not in cytosol)
How does LLO work?
Binds to cholesterol and drives oligomerization, formation of a beta-barrel pore in membrane
What is PIcA and PIcB?
Phospholipase C enzymes that disrupt vacuole membrane
What is Mpl?
Metalloprotease required for PIcB maturation
What is Hpt?
Hexose phosphate transporter (acquires nutrients)
What is an RNA thermometer, and how does it work in PrfA?
At low temp, RNA secondary structure (hairpin loop) blocks the Shine-Delgarno sequence
Hairpin melts at higher temps, allowing the ribosome to bind to mRNA
Temperature activated, post transcriptional regulation of gene expression
