Biofilms

Question 1

What is a biofilm?

Answer 1

Bacteria (and other microorganisms) engulfed in slime made of extracellular polymers

Question 2

What happens after attachment to a surface?

Answer 2

Phenotype changes to produce slime

Question 3

Purposes of slime in biofilm? (2)

Answer 3

1) Biocide resistance

2) Moderation of nutrients, pH/electrical gradients, metabolite retention and extracellular products

Question 4

Colonisation sequence of biofilm?

Answer 4

Bacteria normally primary coloniser

Then yeasts, algae, fungi, protozoa colonise depending on environment

Question 5

What attracts primary coloniser to biofilm?

Answer 5

Carbohydrates

Question 6

Resistance mechanisms of biofilms?

Answer 6

Moist - Prevents desiccation
Phagocyte protection
Different metabolisms may be beneficial for each other
Cross feeding (metabolic products)
Transfer of interspecies genetics
Antibiotic resistant

Question 7

Order of resistant organisms?

Answer 7

1) In biofilm (60-100% more resistant)
2) Grown in biofilm but left
3) Standalone

Question 8

Examples of biofilm locations in the body? (4)

Answer 8

1) Teeth
2) Skin
3) Indwelling devices
4) Internal surfaces

Question 9

Features of biofilm

Answer 9

Varying growth rates
Gradients (nutrients etc)
Cell-cell signalling to up regulate key genes

Question 10

Example of signalling chemicals

Answer 10

N-acyl homoserine lactones

Question 11

Define autoinduction

Answer 11

Product by parent organism upregulates genes in same species

Question 12

Define alloinduction

Answer 12

Product of another organism upregulates genes in different species

Question 13

Mechanisms of surface approach? (3)

Answer 13

Diffusion (random collision)
Motility chemotaxis (flagella, usually attracted to something on surface)
Turbulence (increased chance of collision)

Question 14

What affects surface attachment? (4)

Answer 14

1) Negative charges on bacterial cell and aq. surfaces (repulsion)
2) Changing aq. environment, attachment broken easily
3) Energy required to overcome repulsion
4) Slimes and exopolymers act as a cement

Question 15

Types of biofilm growth? (3)

Answer 15

1) Corncob - Thin, upwards
2) Mushroom - Fluid movement erodes chunks of cells
3) Plaques - Large mass of cells, some empty pockets

Question 16

What affects phenotypes of biofilms?

Answer 16

Nutrient availability and liquid flow

Question 17

Biofilm dispersal methods? (3)

Answer 17

1) Enzymic sloughing - Slime dissolved at periphery, cell chunks removed (lyase enzymes)
2) Physical sloughing - Waves wash against biofilm, reliving chunks of cells
3) Erosion - Singular cells continuously released, change detectable in each sample