Lecture 25 -- Biofilms Flashcards
this type of growth is not associated with planktonic cells/pure cultures, it is the most prevalent mode of growth and is associated with 80% of all infections, makes bacteria 1000x more resistant to antibiotics, and is often considered in chronic infections
biofilm
Antoine van Leeuwenhoek discovered what by noticing that bacteria protected the teeth of animals against vinegar
that biofilms on the surface had a tolerance to antimicrobial agents
communities of bacteria/microorganisms within a matrix
biofilm
What are the four reasons bacteria form biofilms
- defense
- adherence
- close proximity to other cells
- peer pressure
what part of a biofilm is important for adherence and structural support, protection from desiccation/biocides/antibiotics, and evasion of the immune system
matrix
List five things found in the matrix of biofilms
- Polysaccharides
- Proteins
- extracellular DNA
- Signaling molecules
- Water
List the three types of polysaccharides produced by bacteria and their locations
- storage in the cell
- capsular tightly adhered to cell surface
- extracellular necessary for biofilms (ex: xanthan, cellulose, etc)
which exopolysaccharide is involved with cell to cell adhesion, pellicle formation, and is made up of 1–>4 linking of amines
Pel
which exopolysaccharide is important for surface attachment, biofilm structure and maintenance, and is made up of repeating pentasaccharides
Psl
where is pel located
at the periphery/stalk of biofilms
In biofilms, what molecule (or process) is incorporated into lipid A to reduce host inflammatory response
palmitate acyl chain (palmitoylation)
what enhances cell aggregation, attachment, and provides strength to biofilms
amyloids (fibrils)
what contributes a protein component important for initial attachment and matrix stabilization in biofilm formation
it is made up of a two-partner secretion system CdrAB
adhesins
which secretion system releases virulence factors and contains a passenger and translocator
Two-partner secretion (TPS) systems (CdrA & CdrB)
Which passenger virulence factor is a rod shaped protein with a beta helical structure?
CdrA
Which translocator protein is a beta barrel porin
CdrB
Are biofilms homogenous?
No they can vary spatially and temporally and are physiologically distinct from planktonic cells
What is upregulated in biofilm cells
- LPS modifications
- Efflux pumps
- Oxidative stress response
- Adherence
- Genetic competence
What is down-regulated in biofilm formation
- protein synthesis
- pili
- flagella
What happens to oxygen concentrations in biofilms as you get deeper
they decrease
what does structuring the microbial community in a biofilm help with
allows access to more oxygen and other resources
why are biofilms more tolerant to antimicrobials than planktonic cells?
- matrix serves as barrier
- there’s reduces metabolism and growth rates
- they can express efflux pumps and stress response regulons “the biofilm phenotype”
is the “biofilm phenotype” responsible for antibiotic tolerance or resistance and why
tolerance; if the film is disrupted, the bacteria die
which two traditional antibiotic resistance mechanisms are active and upregulated in biofilms
efflux pumps and enzymes that degrade antibiotics
what enzyme was found expressed in P. aeruginosa biofilms
beta-lactamase
Which areas of a biofilm are targeted by aminoglycosides, fluoroquinolones, and tetracyclines?
high activity/surface bacteria
Which areas of a biofilm are targeted by SDS, EDTA, Colistin, and Gallium
The center/dormant bacteria
which cells survive an antimicrobial challenge in a biofilm and why are cells given enough time to initiate a stress response
- the antimicrobial agent does not reach all the cells in a biofilm
- viable cells that are metabolically inactive
what comparison to bacterial biofilm communication can be made?
neurons in the brain
what is the relationship between bacterial density and quorum sensing in bacteria
high bacterial density, high QS signal, increased gene activation or repression
what effect do rhamnolipids have on biofilm architecture
they act as surfactants to disperse the biofilm and prevent spaces/channels from closing
provide an example of how environmental conditions alter biofilm development
different carbon sources can determine whether a biofilm is flat or structured by altering surface motility
List three developmental pathways biofilms can take
- structured
- structured with motile cap forming on immobile stalk
- flat
what do elevated levels of c-di-GMP cause with regard to biofilms
the production of exopolysaccharides and adhesins, DGC activity is increased
what does depleted levels of c-di-GMP cause in biofilms
cells become planktonic and motile (in some cases, PDE activity is increased
List four ways other organisms disrupt biofilms
- lysins, depolymerases
- proteases
- lipases
- nucleases
what do glycoside hydrolases do
degrade and inhibit biofilms
what is a genetic disease that disrupts CFTR (a protein that acts as a channel for the movement of chloride ions in and out of cells), this causes a buildup of mucus
cystic fibrosis
