Term
| How can you tell the difference between E.coli and salmonella by sight? |
|
Definition
|
|
Term
| What test could you perform that would differentiate between Salmonella and E. coli? |
|
Definition
| Salmonella grows pale on MacConkey agar (non lactose fermenting) while E. coli grows red |
|
|
Term
| Which salmonella species cause typhoid fever? |
|
Definition
|
|
Term
| What does S.enteritidis cause and what can that develop into? |
|
Definition
| Enteric fevers, bacteraemias |
|
|
Term
| What are the three important variations of E.coli? |
|
Definition
K12 - non pathogenic lab strain
EHEC/STEC - serious, sometimes lethal
EIEC - causes human gut disease- shigella is a version of this |
|
|
Term
| Why is it odd that Shigella are non motile? |
|
Definition
| They have almost a full set of flagellar genes |
|
|
Term
| What do Salmonella and EIEC use to secrete proteins? |
|
Definition
|
|
Term
| How do the enteric and non enteric bateria invade cells in the gut epithelium? |
|
Definition
enteric - make ordinary epithelial cells take them up
Non enteric- rely on Peyer's patches, which sample gut contents constantly |
|
|
Term
| How does salmonella eneteridis invade gut cells? |
|
Definition
| Secrete effector proteins through the T£ss, causing actin reorganisation in the eukaryotic bowel cells, causing either membrane ruffling or pedestal formation and uptake by host cells. They form an SCV (salmonella containing vacuole) after invasion |
|
|
Term
| What does Salmonella do with the actin it repolymerises? |
|
Definition
| Uses it to form strings to push it from cell to cell |
|
|
Term
|
Definition
| No, just attaches and secretes a toxin |
|
|
Term
|
Definition
| No, sometimes it just attaches w/ pedestals |
|
|
Term
|
Definition
| Enteroaggerative E.coli, have more adhesion factors, clump at gut surface in larger groups, do not invade |
|
|
Term
| What are encoded by SPI and what are they? |
|
Definition
| T3SS, Salmonella pathogenicity islands |
|
|
Term
| What is the basic structure of the T3SS? |
|
Definition
| Hollow core, through which effector molecules are secrted, called a needle complex |
|
|
Term
| What does the SPI1 T3SS secrete? |
|
Definition
| SipB and SipC and SipA, SipB modifies the host cell cytoskeleton,affecting actin polymerisaion so that the bacteria are engulfed by pseudopodia and internalised across the gut wall, SipC is invloved in invasion of the gut cells, SipA staples two actin filaments together, stabilzing the actin filaments around where the bacterium is bound, allowing the membrane ruffling to engulf the bacterium |
|
|
Term
| What is the SPI2 T3SS important for? |
|
Definition
| entering macrophages and spreading from cell to cell |
|
|
Term
| When does secretion of the T3SS occur, when does the complex form, and why is this? |
|
Definition
| pH7.2, pH5, so the complex forms in the vacuole and is ready to secrete as soon as it reaches the cytoplasm |
|
|
Term
| What toxin does EHEC produce? |
|
Definition
|
|
Term
| Which E. coli forms do not cross the gut wall? |
|
Definition
|
|
Term
| What is the structure of Shiga toxins and what encodes them? |
|
Definition
| A and B sununits, genes stxA and stxB |
|
|
Term
| How do Shiga toxins work? |
|
Definition
| The B sununits bind to receptors on the host cell surfaces and deliver the active A subunit of the toxin into those cells. The A subunit must be nicked to activate it. The A subunit then binds to the 60S subunits of ribosomes and nicks the ribosomal RNA to prevent translation |
|
|
Term
| Where do the Shiga toxins travel? |
|
Definition
| Through the gut cells nto the blood stream, round to the kidneys, causing organ damage and potentially death |
|
|
Term
| What receptor does the Shiga toxin target, and where is it found? |
|
Definition
| Gb3, kidney and brain endothelial cells |
|
|
Term
|
Definition
| Enteric bacteria are so recombinogenic that they share genes amongst others in the gut so often, that this gneome is known as the pangenome |
|
|
Term
| What are mutator strains? |
|
Definition
| BActeria that have lost teh ability to rapair DNA, create many new variants, protected by the enzymes of those around them, if new variants are advantageous and taken up by a fit bacterium, may spread |
|
|
Term
| How does Salmonella survive inside the macrophage? |
|
Definition
| Effector molecules modulate the inflammatory response |
|
|
Term
| What does the Salmonella SspH2 protein do? |
|
Definition
| Interferes with the normal ubiquitin pathways of eukaryotic cells - leading to cell death |
|
|
Term
| What is reproduction inside the SCV characterised by? |
|
Definition
| formation of salmonella induced filaments |
|
|
Term
|
Definition
| mimic GEFs, activating host GTPase, stimulating pathways that lead to cytoskelton assembly |
|
|
Term
| how do SipA and SipC affect actin? |
|
Definition
| Promote displacement of actin in the host cytoskelton |
|
|
