Biofilms

Question 1

where do biofilms grow

Answer 1

interfaces

solid: liquid, solid:air, liquid:air, liquid:liquid

Question 2

biofilms aren’t bound to and growing at an interface TF

Answer 2

FALSE

Question 3

When do biofilms form

Answer 3

when MOs attach to surfaces and grow

Question 4

do biofilms bring about any phenotypic change?

Answer 4

yes immediate phenotype change- resistance

Question 5

what is the road of glycocalyx (slime). how soon does this form

Answer 5

forms within minutes

moderates the physio-chemical environment of the MO- anything that wants to get to them has to pass through the slime

Question 6

what charged substances can get through a biofilm? why

Answer 6

positive

as a biofilm tends to be negative

Question 7

biofilms lead to ________ formation. ____ cell density

Answer 7

micro colony

high

Question 8

can a biofilm only contain one species

Answer 8

yes, many hospital infections are single species

Question 9

what type of MOs can be found in biofilms?

Answer 9

bac
yeast 
algae 
fungi 
protozoa

Question 10

what is the primary organism in biofilms?

Answer 10

bacteria

then get further tertiary colonisers

Question 11

biofilms provide protection from what?

Answer 11

dessication- hydrated layer

phagocytes

Question 12

why are biofilms good for the microorganisms nutrient wise?

Answer 12

concentrates them

concentrates extracellular products- one species breakdown things which can be used by other species

Question 13

how can biofilms aid resistance

Answer 13

interspecies genetics- transfer of resistance genes due to being in close proximity

Question 14

how do we treat indwelling device infection with biofilm?

Answer 14

another surgery and replacement of the implant is the only way

Question 15

does a biofilm cover a whole surface?

Answer 15

no can be patchy

Question 16

if a biofilm forms on the inside of a pipe what happens to the flow capacity

Answer 16

decreases- similar situation in arteries

Question 17

3 examples of biofilms associated with indwelling devices?

Answer 17

pacemakers
CNS shunts
catheters

Question 18

do we know why biofilms are so resistant?

Answer 18

not 100% sure

we have 3 theories

Question 19

what are the 3 theories of why biofilms are so resistant?

Answer 19

exclusion
cell-cell signalling
biofilm cells- concentrations

Question 20

explain the theory of exclusion influencing resistance

Answer 20

AM agents cant penetrate the biofilm as easily (can still penetrate)

Question 21

explain the theory of biofilm cells- concentrations influencing resistance

Answer 21

cells on the edge of the biofilm might get killed by an agent but not the ones deeper down
nutrient gradients- deeper in the biofilm there’s less so the bacteria grow slower- this makes them more resistant

Question 22

how does slower metabolism effect resistance?

Answer 22

makes them more resistance as they grow slower

can be due to being deeper in the biofilm therefore less access to nutrients

Question 23

explain how the cell-cell signalling theory can contribute to resistance?

Answer 23

cells communicate when in high cell density (biofilms) using low MW diffusible materials
allows them to up-regulate genes using HSLs

Question 24

what do cells in a biofilm use communicate

Answer 24

low MW diffusible materials

Question 25

what are HSLs?

Answer 25

homoserine lactones

Question 26

what produces HSLs?

Answer 26

almost all gram negative bacteria

Question 27

what are the effects of HSLs building up in a biofilm?

Answer 27

once a threshold concentration is reached, this up regulates genes in the producing organisms: AUTOINDUCTION

Question 28

what is alloinduction

Answer 28

when the HSLs produced by one type of organism, up regulates genes in an unrelated species

Question 29

what is auto induction

Answer 29

HSL production causes upregulation of genes in the producing organism

Question 30

what is the threshold HSL concentration for gene upregulation

Answer 30

depends on the producing organism

Question 31

what is quorum sensing?

Answer 31

population responds on mass - coordinated population response

Question 32

what is quorum sensing key in?

Answer 32

biofilm resistance to AM agents

Question 33

6 steps in biofilm formation

Answer 33

1. arrival at surface 2. irreversible attachment to surface 3. adoption of sessile phenotype 4. biosynthesis of exopolymers 5. upregulation in the production of virulence factors 6. detachment and dispersal

Question 34

what would the cells in the biofilm do if they run out of food?

Answer 34

they would leave and seek a new surface to colonise

Question 35

3 mechanisms a bacterial cell approaches the surface?

Answer 35

diffusion motility chemotaxis turbulence

Question 36

what type of bacteria does diffusion occur in when approaching a surface? process is _____

Answer 36

non motile bacterium | random

Question 37

explain motility chemotaxis

Answer 37

chemotaxis response | smell glucose on a surface and move towards the nutrients

Question 38

what forces hold a bacteria to the surface in reversible binding?

Answer 38

VDW | electrostatic forces

Question 39

what must the bacteria do if they want to irreversibly bind to the surface?

Answer 39

overcome energy barrier

Question 40

what would aid a bacteria to overcome the energy barrier and attach to a surface irreversibly?

Answer 40

projections- the narrower the easier it is to overcome the barrier narrower organism

Question 41

what are projections called in the process of irreversible attachment to surface?

Answer 41

bridging structures- helps them, overcome the barrier

Question 42

what occurs after irreversible binding?

Answer 42

exopolysmer deposition and phenotypic switch

Question 43

what effect does 'exopolysmer deposition' have

Answer 43

re-inforces binding | modulates the environment

Question 44

what leads to micro colony formation?

Answer 44

growth and multiplication

Question 45

what are micro colonies?

Answer 45

small pockets of cells

Question 46

3 types of biofilm phenotypes?

Answer 46

corncobs mushroom plaque like

Question 47

explain how a corncob biofilm grows

Answer 47

thin and upwards quite dramatically

Question 48

explain how a mushroom biofilm grows?

Answer 48

water flows around the biofilm causing it to be top heavy

Question 49

what environments are mushroom biofilms found

Answer 49

aq

Question 50

what are plaque like biofilms like

Answer 50

a thick mass of cells

Question 51

how can plaque turn into a mushroom

Answer 51

increasing turbulence of flow across the population

Question 52

biofilms are ____genou

Answer 52

heterogenous

Question 53

what must you stop to stop succession of biofilms?

Answer 53

the primary colonisers | e.g. higher organisms cannot colonise if the primary colonisers aren't present

Question 54

3 mechanisms of biofilm dispersal

Answer 54

enzymatic sloughing physical sloughing by shear force erosion- cell cycle mediated

Question 55

why would cells want to disperse?

Answer 55

surface gets deprived of nutrients

Question 56

when does enzymatic sloughing occur and how?

Answer 56

under starvation mechanism | production of lyase enzymes which breakdown exopolysaccharides (slime) so chunks of cells can be removed

Question 57

enzymatic sloughing is _____. | continuous or periodic

Answer 57

periodic

Question 58

how does physical sloughing work in regards to dispersal of biofilm

Answer 58

shear force | cells are washed away

Question 59

physical sloughing is difficult to ______

Answer 59

regulate

Question 60

explain cell cycle mediated

Answer 60

events in the cell cycle- erosion events where one cell is released

Question 61

why is cell cycle mediated dispersal from biofilm easy to detect?

Answer 61

happened one at a time | happens continuously