Host- Bacterial Interaction Flashcards
When do microbiota become pathogenic
When breaking through epithelial barriers into sterile areas like blood
In what 4 areas are microbiota found (non sterile)
Skin
Upper respiratory tract
Urinary tract
Intestinal tract
Which layers in things like intestine, respiratory tract are needed for adhesion of bacteria
Mucosal membrane
What are the 3 most important abilities for bacteria to colonise
Motility through flagella
Adhesion- to many surfaces
Growth as a community/biofilm
What are biofilms
Where motile cells adhere to a surface to become sessile and then form a matrix which grows the motile cells count
How is resistance easily passed in a biofilm
Through horizontal gene transfer eg via transposons or integrons
What 4 things does biofilms protect from/ produces
1- protozoan grazing
2- anti microbial chemicals
3- optimum environment
4- immune response of host
How does biofilms protect from antimicrobials
They have persister cells which can move from quiescence to active
They are anti microbial resistant by nature
Eg tolerant to drugs
How do biofilms give an optimum environment
Nutrients supply via water channels
What are water channels for
Allow liquid to flow unwanted materials out
Also allow nutrients to enter biofilms for growth
What are the 5 stages of biofilm production
1- absorption : of motile cells to a surface
2- irreversible attachment : matrix production out of polysaccharides
3- growth : matrix releases growth signals to stimulate growth of bacteria to the surface
4- mature macro colony : many cells are attracted through CHEMOATTRACTANTS
5- dispersion of cells
Which cells attach to the surface to form biofilm
Planktonic mobile cells
What do sessile cells mean
They’ve formed a community and aren’t motile
Which organelles in bacteria are needed for adhesion in biofilms
capsule
What is the importance of a capsule (made of polysaccharides)
1- adhesion to surface in biofilms
2- allows protection in Phagocytosis
3- immunogenic for us
4- production of xantham gum
How does capsule form tissue damage in eg plants
By forming the biofilm
Assembly of which organelles means the bacteria can attach to mucosal barrier
Fimbriae/pili
Which process allows production of fimbriae pili on the outer membrane
Chaperon usher process
The proteins for the fimbriae/pili are produced in cytosol, what allows them to pass into the inner membrane
SEC machine
What happens after the sec machine transfers them into IM
Chaperones allow folding and transfer from periplasm to the FimD transporter
What does the FimD transporter do to the protein
Binds and passes into onto the outside of the OM
What happens when the fimbrial protein is pushed onto outside of OM by the fimD
It can start to produce the fimbrial pili (Fim A)
What adhesin /lectin protein binds to fimA fimbrial pili
FimH
Why is fimH adhesin important
Allows bacteria to bind to host glycan surfaces via their fimbrial pili
What does low shear force binding and high shear force binding mean
Low = bacteria easily detached from host surface
High= stationary bacteria on mucosal surface
Why is there protein secretion out of the bacterial membranes such as enzymes or toxins
It can be used as a defence mechanism or enzymes for energy by degrading surrounding
Give example of an enzyme needed to be secreted for bacterial energy
Amylase which degrades surroundings
Why is protein secretion pathways faster in gram +ve
It can occur in a 1 step process because only 1 membrane
What are the 2 ways proteins move through the inner membrane
1- sec machine : for unfolded proteins
2- tat machine : for folded proteins
What is the differencr between pathogenicity and virulence
Pathogenicity : degree it causes disease
Virulence : factors which allows disease eg toxins, pili, capsid
How can pathogenicity islands through horizontal gene transfer allow disease
They can encode for systems which secrete proteins like toxins
Or
Can encode for fimbriae/pili which allow for pathogenesis (adhesion)
What needs to happen for bacteria to colonise
Break through epithelial barriers
Which 2 ways can bacteria cause disease after breaking epithelial barriers
1- invasion into other cells
2- toxins
What are the 2 types of toxins
1- exotoxins : secreted to environment via secretion pathway
2- endotoxins : toxins stay on surface eg on lipid A of gram negative
Which type of toxin causes fever symptoms but low toxicity
Endotoxins eg pyrogenic toxin from lipid A
What happens to cells if exotoxins are secreted
Lysis
What are AB exotoxins eg cholera
B subunit binds to the cells receptors and conformation change occurs
Allows A subunit of exotoxins to be uptaken into cell
A subunit causes damage to cell
Other than AB exotoxins what other forms are there
Super antigens- overstimulate immunity
Enterotoxins- specific acting on intestine
Neurotoxins - act on cell nerves
Which exotoxins target intestine
Enterotoxins
Why are endotoxins specific to gram -ve
The outer membrane has lipid A and polysaccharides
