Lecture 25 -- Biofilms

Question 1

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

Answer 1

biofilm

Question 2

Antoine van Leeuwenhoek discovered what by noticing that bacteria protected the teeth of animals against vinegar

Answer 2

that biofilms on the surface had a tolerance to antimicrobial agents

Question 3

communities of bacteria/microorganisms within a matrix

Answer 3

biofilm

Question 4

What are the four reasons bacteria form biofilms

Answer 4

• defense
• adherence
• close proximity to other cells
• peer pressure

Question 5

what part of a biofilm is important for adherence and structural support, protection from desiccation/biocides/antibiotics, and evasion of the immune system

Answer 5

matrix

Question 6

List five things found in the matrix of biofilms

Answer 6

1. Polysaccharides
2. Proteins
3. extracellular DNA
4. Signaling molecules
5. Water

Question 7

List the three types of polysaccharides produced by bacteria and their locations

Answer 7

• storage in the cell
• capsular tightly adhered to cell surface
• extracellular necessary for biofilms (ex: xanthan, cellulose, etc)

Question 8

which exopolysaccharide is involved with cell to cell adhesion, pellicle formation, and is made up of 1–>4 linking of amines

Answer 8

Pel

Question 9

which exopolysaccharide is important for surface attachment, biofilm structure and maintenance, and is made up of repeating pentasaccharides

Answer 9

Psl

Question 10

where is pel located

Answer 10

at the periphery/stalk of biofilms

Question 11

In biofilms, what molecule (or process) is incorporated into lipid A to reduce host inflammatory response

Answer 11

palmitate acyl chain (palmitoylation)

Question 12

what enhances cell aggregation, attachment, and provides strength to biofilms

Answer 12

amyloids (fibrils)

Question 13

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

Answer 13

adhesins

Question 14

which secretion system releases virulence factors and contains a passenger and translocator

Answer 14

Two-partner secretion (TPS) systems (CdrA & CdrB)

Question 15

Which passenger virulence factor is a rod shaped protein with a beta helical structure?

Answer 15

CdrA

Question 16

Which translocator protein is a beta barrel porin

Answer 16

CdrB

Question 17

Are biofilms homogenous?

Answer 17

No they can vary spatially and temporally and are physiologically distinct from planktonic cells

Question 18

What is upregulated in biofilm cells

Answer 18

• LPS modifications
• Efflux pumps
• Oxidative stress response
• Adherence
• Genetic competence

Question 19

What is down-regulated in biofilm formation

Answer 19

• protein synthesis
• pili
• flagella

Question 20

What happens to oxygen concentrations in biofilms as you get deeper

Answer 20

they decrease

Question 21

what does structuring the microbial community in a biofilm help with

Answer 21

allows access to more oxygen and other resources

Question 22

why are biofilms more tolerant to antimicrobials than planktonic cells?

Answer 22

• matrix serves as barrier
• there’s reduces metabolism and growth rates
• they can express efflux pumps and stress response regulons “the biofilm phenotype”

Question 23

is the “biofilm phenotype” responsible for antibiotic tolerance or resistance and why

Answer 23

tolerance; if the film is disrupted, the bacteria die

Question 24

which two traditional antibiotic resistance mechanisms are active and upregulated in biofilms

Answer 24

efflux pumps and enzymes that degrade antibiotics

Question 25

what enzyme was found expressed in P. aeruginosa biofilms

Answer 25

beta-lactamase

Question 26

Which areas of a biofilm are targeted by aminoglycosides, fluoroquinolones, and tetracyclines?

Answer 26

high activity/surface bacteria

Question 27

Which areas of a biofilm are targeted by SDS, EDTA, Colistin, and Gallium

Answer 27

The center/dormant bacteria

Question 28

which cells survive an antimicrobial challenge in a biofilm and why are cells given enough time to initiate a stress response

Answer 28

- the antimicrobial agent does not reach all the cells in a biofilm - viable cells that are metabolically inactive

Question 29

what comparison to bacterial biofilm communication can be made?

Answer 29

neurons in the brain

Question 30

what is the relationship between bacterial density and quorum sensing in bacteria

Answer 30

high bacterial density, high QS signal, increased gene activation or repression

Question 31

what effect do rhamnolipids have on biofilm architecture

Answer 31

they act as surfactants to disperse the biofilm and prevent spaces/channels from closing

Question 32

provide an example of how environmental conditions alter biofilm development

Answer 32

different carbon sources can determine whether a biofilm is flat or structured by altering surface motility

Question 33

List three developmental pathways biofilms can take

Answer 33

- structured - structured with motile cap forming on immobile stalk - flat

Question 34

what do elevated levels of c-di-GMP cause with regard to biofilms

Answer 34

the production of exopolysaccharides and adhesins, DGC activity is increased

Question 35

what does depleted levels of c-di-GMP cause in biofilms

Answer 35

cells become planktonic and motile (in some cases, PDE activity is increased

Question 36

List four ways other organisms disrupt biofilms

Answer 36

- lysins, depolymerases - proteases - lipases - nucleases

Question 37

what do glycoside hydrolases do

Answer 37

degrade and inhibit biofilms

Question 38

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

Answer 38

cystic fibrosis