MFD.07 Flashcards
Describe a planktonic culture of cells
+e.g.
homogenous (same nutrients throughout &species) , single species, nutrient rich, • Uniform growth rate
• Even distribution of O2, nutrients, waste etc
• Cells well-separated
• No extracellular matrix
e.g. in a beaker
Describe a surface-associated culture of cells
+e.g.
limited heterogeneity, single species, nutrient rich e.g. petri dish
Describe a natural culture of cells
+e.g.
heterogenous, mixed species, nutrient limited e.g. clay wall
What is a biofilm?
A community of microbial cells encased within a matrix of polymers and associated within an interface. In nature, most bacteria grow in biofilms.
Give an example of a heterogenous culture?
biofilm
Compare species of planktonic culture vs “natural” growth:
planktonic: single species
other: mixed
Compare growth rate of planktonic culture vs “natural” growth:
planktonic: uniform
other: mixed
Compare distribution of O2, nutrients, waste etc of planktonic culture vs “natural” growth:
planktonic: even
other: uneven
Compare position of cells of planktonic culture vs “natural” growth:
planktonic: well-seperated
other: in close contact
Give an example of “Natural” growth
biofilm
True or false
Bacteria in biofilms from those in broth cultures.
true
Compare resistance to antibiotic of biofilm bacteria and planktonic cells
biofilm bacteria are 1000 times more resistant then planktonic
Can bacterial communities be more pathogenic than pure cultures?
yes
Why is there such a range of bacteria in biofilms?
1) Hides most bacteria from host immune system
2) provides niches e.g. anaerobic environments
Where are biofilms found?
(3)
e.g.*3 e,g. location
Anywhere where there is:
An interface
Moisture
Nutrients/energy source
e.g.
Air-liquid interfaces, surfaces of ponds, oceans
Air-solid interfaces, tree trunks, rocks, soil particles
Solid-liquid interfaces, internal surfaces of pipes(including dental unit waterlines), catheters, teeth
What are the 4 stages of a biofilm?
- attachment ( adhesion of a few motile cells to a suitable solid surface)
- colonization (intercellular communication, growth, and polysaccharide formation)
- Development (more growth and polysaccharide
- Active Dispersal (triggered by environmental factors such as nutrient availability)
Why are nutrients non-uniformly distributed in a biofilm?
the matrix impedes mass transfer
What forms the biofilm matrix?
macromolecules from the basic structure and small molecules are trapped within matrix
What macromolecules form the basic structure?
polysaccharides, proteins,nucleic acids
What small molecules may trapped within the matrix of a biofilm?
- Nutrients
- Metals
- signalling molecules
What are the 4 diagnostic tools to proving a biofilm infections?
• Pathogenic bacteria are associated with a surface.
• Direct examination of infected tissue demonstrates aggregated cells in cell
clusters encased in a matrix, which may be of bacterial and host origin.
• Infection is confined to a particular site in the host.
• Recalcitrance to antibiotic treatment despite demonstrated susceptibility of
planktonic bacteria. (planktonic bacteria are less susceptible to antibiotic when in biofilm)
Recalcitrance basically means the same as…
reistance
Why are biofilm bacteria so resistant?
- Slow growing
- Presence of dormat (“persister”) cells
- Sequestration (=seperation) from the immune system
- Elevated expression of efflux pumps.
- Poor penetration of antibiotics.
What type of antibiotic is effected by the fact that biofilm bacteria are sequestered from the immune system?
bacteriostatic antibiotics that work in conjunction with host immunity)
