Host- Bacterial Interaction

Question 1

When do microbiota become pathogenic

Answer 1

When breaking through epithelial barriers into sterile areas like blood

Question 2

In what 4 areas are microbiota found (non sterile)

Answer 2

Skin

Upper respiratory tract

Urinary tract

Intestinal tract

Question 3

Which layers in things like intestine, respiratory tract are needed for adhesion of bacteria

Answer 3

Mucosal membrane

Question 4

What are the 3 most important abilities for bacteria to colonise

Answer 4

Motility through flagella

Adhesion- to many surfaces

Growth as a community/biofilm

Question 5

What are biofilms

Answer 5

Where motile cells adhere to a surface to become sessile and then form a matrix which grows the motile cells count

Question 6

How is resistance easily passed in a biofilm

Answer 6

Through horizontal gene transfer eg via transposons or integrons

Question 7

What 4 things does biofilms protect from/ produces

Answer 7

1- protozoan grazing
2- anti microbial chemicals
3- optimum environment
4- immune response of host

Question 8

How does biofilms protect from antimicrobials

Answer 8

They have persister cells which can move from quiescence to active
They are anti microbial resistant by nature

Eg tolerant to drugs

Question 9

How do biofilms give an optimum environment

Answer 9

Nutrients supply via water channels

Question 10

What are water channels for

Answer 10

Allow liquid to flow unwanted materials out

Also allow nutrients to enter biofilms for growth

Question 11

What are the 5 stages of biofilm production

Answer 11

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

Question 12

Which cells attach to the surface to form biofilm

Answer 12

Planktonic mobile cells

Question 13

What do sessile cells mean

Answer 13

They’ve formed a community and aren’t motile

Question 14

Which organelles in bacteria are needed for adhesion in biofilms

Answer 14

capsule

Question 15

What is the importance of a capsule (made of polysaccharides)

Answer 15

1- adhesion to surface in biofilms
2- allows protection in Phagocytosis
3- immunogenic for us
4- production of xantham gum

Question 16

How does capsule form tissue damage in eg plants

Answer 16

By forming the biofilm

Question 17

Assembly of which organelles means the bacteria can attach to mucosal barrier

Answer 17

Fimbriae/pili

Question 18

Which process allows production of fimbriae pili on the outer membrane

Answer 18

Chaperon usher process

Question 19

The proteins for the fimbriae/pili are produced in cytosol, what allows them to pass into the inner membrane

Answer 19

SEC machine

Question 20

What happens after the sec machine transfers them into IM

Answer 20

Chaperones allow folding and transfer from periplasm to the FimD transporter

Question 21

What does the FimD transporter do to the protein

Answer 21

Binds and passes into onto the outside of the OM

Question 22

What happens when the fimbrial protein is pushed onto outside of OM by the fimD

Answer 22

It can start to produce the fimbrial pili (Fim A)

Question 23

What adhesin /lectin protein binds to fimA fimbrial pili

Answer 23

FimH

Question 24

Why is fimH adhesin important

Answer 24

Allows bacteria to bind to host glycan surfaces via their fimbrial pili

Question 25

What does low shear force binding and high shear force binding mean

Answer 25

Low = bacteria easily detached from host surface

High= stationary bacteria on mucosal surface

Question 26

Why is there protein secretion out of the bacterial membranes such as enzymes or toxins

Answer 26

It can be used as a defence mechanism or enzymes for energy by degrading surrounding

Question 27

Give example of an enzyme needed to be secreted for bacterial energy

Answer 27

Amylase which degrades surroundings

Question 28

Why is protein secretion pathways faster in gram +ve

Answer 28

It can occur in a 1 step process because only 1 membrane

Question 29

What are the 2 ways proteins move through the inner membrane

Answer 29

1- sec machine : for unfolded proteins

2- tat machine : for folded proteins

Question 30

What is the differencr between pathogenicity and virulence

Answer 30

Pathogenicity : degree it causes disease

Virulence : factors which allows disease eg toxins, pili, capsid

Question 31

How can pathogenicity islands through horizontal gene transfer allow disease

Answer 31

They can encode for systems which secrete proteins like toxins

Or

Can encode for fimbriae/pili which allow for pathogenesis (adhesion)

Question 32

What needs to happen for bacteria to colonise

Answer 32

Break through epithelial barriers

Question 33

Which 2 ways can bacteria cause disease after breaking epithelial barriers

Answer 33

1- invasion into other cells

2- toxins

Question 34

What are the 2 types of toxins

Answer 34

1- exotoxins : secreted to environment via secretion pathway

2- endotoxins : toxins stay on surface eg on lipid A of gram negative

Question 35

Which type of toxin causes fever symptoms but low toxicity

Answer 35

Endotoxins eg pyrogenic toxin from lipid A

Question 36

What happens to cells if exotoxins are secreted

Answer 36

Lysis

Question 37

What are AB exotoxins eg cholera

Answer 37

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

Question 38

Other than AB exotoxins what other forms are there

Answer 38

Super antigens- overstimulate immunity

Enterotoxins- specific acting on intestine

Neurotoxins - act on cell nerves

Question 39

Which exotoxins target intestine

Answer 39

Enterotoxins

Question 40

Why are endotoxins specific to gram -ve

Answer 40

The outer membrane has lipid A and polysaccharides