Biofilms

Question 1

Impact of biofilms

Answer 1

Bioremediation and bio transformation processes eg wastewater treatments)
BUT
fouling of hydroelectric, water reticulation, heat exchange, and food processing pipelines
>70% of infections
Increase resistance

Important to understand prevention and enhancement perspectives

Question 2

Environmental impacts of biofilms

Answer 2

Sites for major microbial activities eg carbon production, mineralisation
Catalysts for adaptation and evolutionary events eg gene transfer and provision of unique selective pressures
Biodegradation

Question 3

Industrial impacts of biofilms

Answer 3

Marine fouling
Fouling of hydroelectric, water reticulation, heat exchange and food processing pipelines
Corrosion of metal surfaces
Waste water treatment
Trickling filters
Activated sludge
Fluidised bed reactors
Bioremediation

Question 4

Microbiologically influenced corrosion

Answer 4

Biocorrosion caused by bacteria results in putting, crevices corrosion and stress corrosion cracking

Question 5

Wastewater treatment (steps)

Answer 5

Primary - removal of large objects
Secondary - activated sludge, trickling filter (encourage biofilm growth on rocks and plastic), biofilms, bacteria convert dissolved or suspended solids to settleable solids
Tertiary - biological or chemical removal of nitrate, ammonia and phosphates, virus removal, trace chemical removed

Question 6

Medical and dental biofilm impacts

Answer 6

Dental plaque
Chronic wounds - low oxygen in biofilm niches, bacteria protected from topical agents, impaired migration and proliferation of keratinocytes, defences unable to clear infection
Cystic fibrosis
Medical implants

Question 7

Biofilm

Answer 7

Microbial sessile community characterised by cells that are irreversibly attached to substratum, interface or to eachother, embedded in a self produced matrix of extracellular polymeric substances (EPS) and in comparison to planktonic cells, they exhibit altered phenotypes eg growth rate and gene transcription

Heterogeneity in space and time
Microconsortia
High biodiversity
Retention of exoenzymes, nucleus acids
Increased resistance

Question 8

Biofilm life cycle

Answer 8

Planktonic cells
Early reversible attachment
Irreversible attachment
Start production of eps
Maturation
Passive detachment and active dispersal

Question 9

Channels in biofilms

Answer 9

Release of surfactants causes this

Question 10

Extracellular polymeric substances (EPS)

Answer 10

Boo polymers if microbial origins
Polysaccharides
Proteins
Glycoproteins, phospholipids, LPS
Nucleic acids

EPS fundamentally influence biofilm cell microenvironment

Question 11

Visualisation of alginate in P. aeruginosa biofilms using flourescently labelled ConA

Answer 11

Sugars (polysaccharides) present in mucoid strains but not in non mucoid strains
Mucoid mosaic structure, non mosaic flat and sheet like

Question 12

Evolution of biofilm research

Answer 12

Biofilm life cycle
Differentiation in biofilms
Multicellular traits
Communication (quorum sensing)
Dispersal if biofilm cells
Recolonisation

Question 13

Differentiation in biofilms

Answer 13

Multi species
Different parts of biofilm does different jobs

Bacterial biofilms effluents are auto toxic at time of cell death - release nutrients for remaining cells

Question 14

Multicellular traits in biofilms

Answer 14

Sacrifice for greater good
Structurally - bacillus subtilis will clump together similar to biofilms

Question 15

Communication (quorum sensing)

Answer 15

Release key molecules to effect behaviour of other parts of biofilm. Can happen across species
AHL (aka AI-1) mediated regulation in gram negative bacteria
AI2 signalling system in gram negative and positive bacteria
Peptide mediated regulation in gram positive bacteria

Question 16

AHL mediated biofilm formation

Answer 16

Rhizobium sp - modulation
Agrobacterium tumefaciens - colonisation
Erwinia carotovora - biofilm formation, exoenzyme production and invasion of plant tissue

Question 17

AI-2

Answer 17

Ecoli - biofilm formation
Vibrio cholerae - biofilm formation
Bacillus subtilis - biofilm formation

Question 18

Quorum sensing blockers

Answer 18

Can this stop biofilm formation?
Eg cystic fibrosis

Question 19

Dispersal of biofilm cells and recolonisation

Answer 19

Spread of “infection”
Phenotypic variation in dispersal cell populations
biofilms have different colony variants

Question 20

Applications of biofilm knowledge

Answer 20

Treatment of biofilms in industrial, environmental and medical settings with auto toxic compounds
Quorum sensing blockers
Addition of compounds that induced early dispersal eg nitric oxide

Question 21

Reversible and irreversible attachment

Answer 21

Forces that operate over long distances (5-20nm) and short distances (0.2-2nm)

Wan der waals forces, repulsive electrostatic forces and polymer bridging

Question 22

10-20mm

Answer 22

Repulsive electrostatic interactions

Question 23

2-10nm

Answer 23

Repulsive and attractive electrostatic interactions

Question 24

0.5-2nm

Answer 24

Interfacial water is a barrier But can be removed by hydrophobic groups
So polymer bridging

Question 25

Attachment at long distances (5-20nm)

Answer 25

Van Der waals Reversible binding Little energy needed to remove bacteria eg spinning of flagellum DLBO theory - applies to all particles in liquid

Question 26

Attachment at short distances (0.2-2nm)

Answer 26

Non specific and specific binding Binding mediated by polymer bridging, achieved by reduced radius of body Irreversible binding Does not happen with all colloidal particles

Question 27

Polymers in combed in specific irreversible adhesion

Answer 27

Surface structures that allow polymer bridging eg Exopolymers Fimbriae Stalks Flagella Lipoteichoic acids (LTA) LPS Surfaced localised proteins and pigments A layers S layers

Question 28

Two types of binding using surface structures for polymer bridging

Answer 28

Non specific irreversible- hydrophobic interaction, ion-, hydrogen, Convalent binding Specific irreversible adhesion (key and lock) - defined as structure mediated binding that can be blocked by analogue

Question 29

Key lock mediated adhesion

Answer 29

Pili or fimbriae Afimbrial adhesion - attachment through receptors

Question 30

Fimbriae mediated binding

Answer 30

Large variations in fimbriation between species Consist of identical protein subunits held together by H-bonds and hydrophobic interaction Flexible Fimbriae have many subunits/turn (fibrillae) Rigid Fimbriae have fever subunits/turns

Question 31

Ecological advantages of Fimbriae

Answer 31

Gene clusters on plasmids Phase variation = individual cells switch between expression and non expression

Question 32

Key lock binding often occurs on living surfaces because:

Answer 32

Epithelial cells expose lipids, proteins and mucus layers These have receptor sites (carbohydrates, peptide sequences)

Question 33

FimH

Answer 33

Bacteria Achesin on e.coli Binds e.coli pili to host monocytes and epithelial cells