Lecture 12 Flashcards
What are three basic mechanisms of invasion? What is an example of a pathogen for each mechanism?
- Interaction with host surface proteins. This requires active participation between both bacteria and host cell. e.g. Listeria
- Injection of bacterial effectors into cytosol. Active participation of baccie and host. e.g. Salmonella
- Active penetration into the host cell. Requires active participation of parasite only. e.g. Toxoplasma
What are three roles of invasion?
- Access to an environment suitable for growth
- Protection from host antibody response
- Traverse anatomical barriers
What anatomical barriers does Listeria cross in the human body?
Intestinal cells to get into the body.
Blood brain barrier to cause meningoencephalitis
Fetal/placental barrier to cause abortion
What is the protein adhesin and receptor for listeria?
Protein adhesin- InIA
Receptor- E-Cadherin
What is internalisation of Listeria driven by? How does it work?
Highly localised changes in the host F-actin cytoskeleton. Actin cytoskeleton surrounds the bacteria on the cell surface and creates a membrane around it, brining it into the cell.
What cells do Listeria infect?
How do macrophages assist in systemic infections caused by Salmonella enterica?
Macrophages eat the bacteria and travels in the blood. The bacteria can then cause systemic infections of the spleen, liver, bones and gall bladder.
What is ‘ruffling’ and how does it work?
Ruffling is named after the appearance of the cell surface when Salmonella enterica is being internalised into the cell. It is caused by large re-modelling of the host cells actin cytoskeleton which is regulated by G proteins.
Eukaryotic Ras family G proteins are active when bound to BLANK and inactive when bound to BLANK.
Eukaryotic Ras family G proteins are active when bound to GTP and inactive when bound to GDP.
What are GAPs and GEFs? What reaction do they catalyse?
GAP- GTPase activating protein
GEF- Guanine-nucleotide exchange factor
How do GAPs and GEFs assist in the internalisation of Salmonella enterica?
Salmonella injects GAFs and GEFs into the gastro epithelial cell.
This activates the ruffling process to internalise the bacterial cells.
GAPs are activated once the cells have been internalised to stop the ruffling process.
What is Toxoplasma gondii?
- what disease does it cause in humans
- what is its usual host
- how do humans usually obtain this pathogen
A parasite
causes encephalitis in immunocompromised and abortions in pregnant women
usual host is cats
humans usually get this after ingesting cysts in undercooked meat or oocysts in cat faeces
True or false- Toxoplasma gondii can only sexually reproduce in human epithelial cells
False- can only sexually reproduce in the cat gut
How do Toxoplasma gondii carry out gliding motility? What other paraside can move by gliding motility?
Gliding motility is driven by the actin and microtubule cytoskeletons of the parasite. Movement of actin filaments causes movement on the receptor proteins that theyre connected to the host cell with. This causes the parasite to move.
Plasmodium (malaria parasite)
