Bacterial strategies for host colonisation Flashcards
What are the 4 attributes involved in a effective host colonisation? ( these can be classified as virulence factors
Adhere to the host cell and resist physical removal
Invade host cells
Compete for iron and other nutrients
Evade the immune system
What do Fimbriae and Pili promote/ where are they mostly found/ what do they bind to/ what is pili made of?
Gram -ve pathogens
Found in virtually all Gram -ve bacteria but not in many Gram +ve bacteria
Made up of a protein called pilin
Bind to sugar receptors on the surface of eukaryotic cells
What does Adhesins enable/ where are they found?
Found in Gram positive bacteria
It enables attachment and resistance to physical removal
What are the functions of M protein?
Resistance to phagocytosis, adherence to epidermal keratinocytes, microcolony formation and invasion of epithelial cells
What is the function of fibronectin?
Has major fucntions in cellular adhesion, differentiation and growth migration.
What is the function of fibronectin in bacteria? How is it activated? (What does it bind to)
Promotes attachment to and infection of host cells
Protein F binds to fibronectin
Lipoteichoic acid binds to fibronectin on epithelial cells
Motility helps to colonisation at mucosal surfaces, What Gram pathgen is it mostly found in, Where is this mechanism mostly used in, Give an example of a bacteria and explain how it changes its surrounding to survive in the gut?, What virulence factor is this?
Gram negative
Colonises the gut
Flagella help move the bacteria through the mucus attach to gut epithelial cell
Urease produced in bacterial cytosol produces ammonia from urea
Ammonia passes into the periplasmic space creating a buffer against acidic pH of the gut, so bacteria survives.
Helicobacter pylori
Resist physical removal
What are invasins and what do they facilitate?
They are molecules that activate the host cells cytoskeleton and promte cell entry by phagocytosis
it faacilitates the growth and spread of the pathogens
What does the bacteria gain when inside the host? (2)
Provide the bacterium with ready supply of nutrients
Protect the bacteria from complement, Ab and other body defence molecules
Give an example of a bacteria that uses a injection mechanism that promotes phagocytosis? Describe in simple words what happens?
Escherichia coli
Bacteria secretion systems co-opt the fuctions of the host cell
Injectosome (needle like receptor) injects the cell membrane of the host releasing effector molecules
These molecules interfere with the cytoskeleton which then encourage phagocytosis
Eventual cell to cell spread.
Basically hijacking the machinery and allowing the bacteria to enter the host without being detected
What are the 3 main nutrients needed for bacterial growth?
Carbon
Nitrogen
Iron
Why is iron important for bacterial growth?
Important for enzyme active properties
Describe the mechanism of iron theft. (4)
Iron is insoluble in the host
Its carried in complexes with glycoproteins
Siderophore is a very strong molecule which will rip the iron from molecules such as lactoferrin and transferrin whcih normaly would release the iron into the host cell (Transferrin found in the serum, lactoferrin found in mucus/sweat/saliva etc.)
The stolen iron will then bind to the siderophore receptor which then will transport the iron into the bacteria
The iron in haemoglobin will be released into the bacteria without any other molecules.
Describe the action of coagulase and give an example of a bacteria that uses it.
Staphylococcus aureus
Coagulase causes fibrinogen—>fibrin which causes clotting
Coagulase is almost always assocaited with pathegenic strains
What is the function of lysozymes and how do some bacteria mutated to protect themself from it?
Lysozymes have the ability to hydrolyse linkages between N-acetylmuramic acid and 2-acetyl-amino-2-deoxy-D-glucose residues
Gram +ve cells are particular vulnerable
N-deacetylation has shown to protect bacteria from lysozymes
