2. Biofilms

Question 1

Define a biofilm

Answer 1

A biofilm is a multi-layered bacterial population embedded in a polysaccharide matrix and irreversibly attached to an inert or living surface. The most common type of bacterial growth found in nature.

Question 2

Describe the mechanisms of biofilm tolerance?

Answer 2

The tolerance of biofilms to antibiotics is multi factorial involving physical, physiological and genetic determinants.

Antimicrobial depletion, slow penetration, stress response, altered micro environment.

Question 3

Detail the steps of biofilm formation

Answer 3

1. Substratum pre conditioning by ambient molecules
2. Cell deposition
3. Cell absorption
4. Desorption
5. Cell to cell signalling and onset of exopolymer production
6. Connective and diffusion transport of CO2 + nutrients
7. Replication and growth
8. Secretion of p0olysaccharide matrix
9. Detachment, erosion and sloughing

Question 4

4. What properties of bulk fluid will have an impact on biofilm formation?

Answer 4

• Flow velocity
• PH: acidic pH stops microorganisms
• Temperature: too hot or cold will slow growth
• Cations
• Antimicrobial agents: clean things and make it harder for attachment

Question 5

5. Why does the presence of biofilms increase the possibility of contamination of water supplies?

Answer 5

• Bacteria and fungi have resistance to Antimicrobial used in water treatment
• Biofilms are aggregates of microorganisms attached to surfaces that can (re)contaminate water by releasing microorganisms

Question 6

What is the chemical nature of the biofilm matrix?

Answer 6

Hydrated extracellular polymeric substances of mostly polysaccharides, but also proteins, nuclei acids and lipids.

Question 7

Why might a biofilm be a good habitat for bacterial cells living in a flowing system?

Answer 7

Biofilms offer bacteria several ecological and physiological advantages; biofilms constitute a protective physical barrier to nonspecific and specific host defences during infection as well as confer tolerance to Antimicrobial agents by reducing diffusion of those toxic compounds.

Question 8

How can biofilms complicate the treatment of infectious diseases?

Answer 8

Bacterial biofilms cause chronic infections because they show an increased tolerance to antibiotics and disinfectant chemicals as well as resisting phagocytosis and other components of the body’s defence system

Question 9

Detail the four applications of biofilms

Answer 9

Industrial production of bio chemicals - biofilm reactors have been used to produce ethanol, but all, lactic acid

Metal recovery through bioleaching - conversion of insoluble metal suffices to water soluble metal surfaces using microbes

Wastewater treatments - aid in the cleansing of wastewater in trickling systems where rocks have been colonised by bacteria and fungi to form biofilm around the rocks

Question 10

Describe the link between legionnaires disease and biofilms

Answer 10

Legionella pneuomophilia causes legionnaires disease

- lives happily in waterways
- can be isolated from air conditioning
- very resistant to Antimicrobia;s
- infection occurs when clumps of the biofilm containing legionella sp are broken and released into the 	air