Topic 1-3 Flashcards
What is a biofilm?
An organized community of bacteria adhered to a surface and surrounded by EPS.
What is are extracellular polymeric substances?
AKA EPS
Comprised of polysaccharides, proteins and nucleic acids
How many different species are in a biofilm?
Can be one, can be many, depending.
What is quorum sensing?
Coordinated chemical signaling between cells.
When does a biofilm form?
When the local concentration of autoinducers reaches a threshold - this initiatesa signaling cascade, modulating gene expression and bacterial physiology to encourage community development
What signaling molecules are used in quorum sensing?
autoinducers
Steps of biofilm formation?
1) Adherence of bacteria to surface
2) Growth & production of EPS (which results in stronger attachment; may be irreversible)
3) Dispersion of single cells from biofilm
What does planktonic mean?
It refers to single bacterial cells NOT in a biofilm
How does the bacterial behaviour change in a biofilm?
Bacteria behave as a group (sense/respond to stimuli in coordinated manner)
How does biofilms change the physiology of bacteria?
Bacteria inside behave differently that those outside, due to different oxygen and nutrient availability
Why are biofilms so important in nature?
It is because that is the behaviour of bacteria in nature - thus studies of planktonic bacteria is a biased view of microbial live
What are some examples of biofilms?
Environmental biofilms (can cause problems like corrosion)
Pathogenic biofilms on implanted medical devices (ex. catheters, dialysis equipment, dental implants)
Pathogenic biofilms on human body surfaces (ex. on the teeth)
Environmental biofilms that impact human health (ex. contaminated drinking water)
Are benign biofilms truely benign?
NO - they can attract, recruit, and concentrate pathogenic bacteria that wouldn’t form biofilms on their own.
How do biofilms increase antimicrobial resistance?
- EPS matrix block the penetration of antimicrobial agents (and can block phagocytosis)
- Nutrient and O2 gradient results in some bacteria being less metabolically active, which makes antibiotics less effective against them (the less metabolically active bacteria)
- “persister” cells keeping biofilm alive
What are some approaches to circumventing biofilms (in therapeutics)
- Interfering with EPS synthesis (ex. coating medical devices w/ chemicals that inhibit matrix formation)
- Inhibiting biofilm adherence (so stopping it from sticking, after it forms)
- Inhibiting autoinducers (to prevent bacteria from forming a biofilm in the first place)
