Lecture 5

Question 1

What are biofilms?

Answer 1

• Conditioning firm of organic and inorganic particles
• Bacteria arrive on surface
• Bacteria attach (reversible/irreversible)
• Biosynthesis of matrix

Question 2

3 ways bacteria bind to surface

Answer 2

Diffusion
Motility chemotaxis
Turbulence impaction

Question 3

Arrival of bacteria to surface layers

Answer 3

• Flow of fluid or air
• Boundary layer (no flow)

Surface

Question 4

laminar flow

Answer 4

Bacteria on separate layers

The boundary layer is not affected (no flow)

Question 5

Turbulent flow

Answer 5

Lots of mixing between bacteria

Boundary layer disturbed

Question 6

How is turbulent flow made greater

Answer 6

Rough surfaces

Question 7

Brownian movement

Answer 7

30-100nm from surface as negatively charged surfaces repel

Question 8

Bridging structures

Answer 8

Generic adhesions - flagella, fimbriae, pili, stalks, teichoic acids

Question 9

Are brownian movement and bridging sturctures reversibly or irreversibly bound?

Answer 9

Reversibly bound

Question 10

Name generic adhesions

Answer 10

Pili, fimbriae, flagella, teichoic acids etc

Bind specifically or non-specifically

Specifically - pathogenic bacteria, some non-pathogenic bacteria, mainly glycoprotein receptors

Non-specifically - Electrostatic forces (abiotic surfaces + conditioning film)

Question 11

What are teichoic and lipoteichoic acids made of?

Answer 11

Fibronectin - Glycoprotein (mannose)

Question 12

What do flagella bind to?

Answer 12

Toll-like receptor 5

Question 13

What specific sugars are found in glycoprotein receptors

Answer 13

Mannose - Vibrio chloerae, Escherichia coli

Galactose - Neisseria gonorrhoeae, Bordetella pertussis

Fucose - Vibrio cholerae

Glucosamine - Neisseria gonorrhoeae

Question 14

What are attachment proteins?

Answer 14

• Sugar-binding proteins
• Encoded in plasmids
• Sugar residues in host receptors - glycans, glycoproteins, and glycolipids

Question 15

What are the attachment proteins for Yersinia, Salmonella, and Neisseria?

Answer 15

YadA

SadA

NadA

Question 16

Attachment proteins for E. coli and Haemophilus influenze?

Answer 16

Hia and Hsf proteins

EibA-G protein

Question 17

Gram positive attachment proteins

Answer 17

Group A Streptococci - Protein M

S. aureus - protein A

C. difficile - CbpA

Question 18

Name examples of irreversibly bound bacteria to surface mechanisms

Answer 18

Phenotypic switch

Exopolymer deposition

Cemented

Question 19

Reversible to irreversible attachment

Answer 19

• Attachment and adhesions form clusters
• Cell communication after enough cells have clustered
• alg - Important gene
• Over-secrete alginate to form slime
• Cements cells to surface
• Mature Biofilm forms via in-house division

Question 20

Cell-cell signalling

Answer 20

Synthesis -> Recognition -> Response

Gram +ve - Oilgopeptides used
Gram -ve - AHLs or HSLs used

Question 21

N-Acyl-Homoserine Lactones types

Answer 21

OHHL (OC6) - Erwinia and Yersinia

BHL (C4) - P. aeruginosa

OdDHL (OC12) - P. aeruginosa

Question 22

Cell signalling in same species cells

Answer 22

Low HSL conc
Below threshold conc
No co-ordinated response

High HSL conc
Above threshold conc
Co-ordinated response

Question 23

Other name for threshold density

Answer 23

Quorum

Question 24

What does Allvibrio and Photobacterium fisheri show?

Answer 24

Bioluminescence

Question 25

What do LuxR and LuxI encode?

Answer 25

Regulatory genes LuxR - Activator proteins LuxI - HSLs Promoters for both operons

Question 26

What does Lux A-E encode for?

Answer 26

Structural genes Light production

Question 27

What do LuxI operons cause

Answer 27

- When sessile, 50-60 changes in gene expression - Down-regulation of planktonic genes - Up-regulation or new expression of beneficial genes e.g. extracellular polysaccharides, antibiotic production, virulence factors

Question 28

What are some species with LuxI/LuxR homologues?

Answer 28

1. Vibrio cholera 2. E. coli H2 3. P. aeruginosa

Question 29

What is a mature biofilm matrix made from?

Answer 29

~98% water ~2-5% cells

Question 30

Exopolymeric substances

Answer 30

Absorbed materials - Nutrients, waste Biosynthetic microbial polymers - Extracellular polysaccharides, nucleic acid, proteins, glycoproteins, phospholipids

Question 31

What do exopolymeric substances do?

Answer 31

- Cellular cement - Form matrix framework - Provide structure - Defined architecture to biofilms

Question 32

Where is there higher bacterial growth and EPS production in biofilms?

Answer 32

Layers closer to nutrients

Question 33

Biofilm topography

Answer 33

- Low flow rate - Slow growth, compact - Most biofilms - High flow rate - Rapid growth, prone to sloughing - Unstable

Question 34

Sloughing

Answer 34

Turbulence, scouring and direct or indirect grazing of biofilm

Question 35

Programmed detachment

Answer 35

- Synchronised liberation of daughter cells - More hydrophilic - Down regulation of high mwt LPS - Leaves low mwt LPS - Shot out of the biofilm - 2-3 division before attachment

Question 36

What are cells embedded in biofilm matrix protected from?

Answer 36

- Desiccation - Starvation - Poisoning - Predation - Colonisation

Question 37

Are bacteria close in biofilms

Answer 37

Yes, with pooled extracellular enzymes and greater resistance to antimicrobial compounds

Question 38

Why are biofilms more difficult to kill?

Answer 38

- Stress tolerance - Less diffusion in matrix - Can require 1000x high conc of antimicrobial agent