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Microbio & Biofilms > Biofilms > Flashcards

Biofilms Flashcards

1
Q

Impact of biofilms

A

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

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2
Q

Environmental impacts of biofilms

A

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

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3
Q

Industrial impacts of biofilms

A

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

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4
Q

Microbiologically influenced corrosion

A

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

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5
Q

Wastewater treatment (steps)

A

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

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6
Q

Medical and dental biofilm impacts

A

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

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7
Q

Biofilm

A

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

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8
Q

Biofilm life cycle

A

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

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9
Q

Channels in biofilms

A

Release of surfactants causes this

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10
Q

Extracellular polymeric substances (EPS)

A

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

EPS fundamentally influence biofilm cell microenvironment

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11
Q

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

A

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

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12
Q

Evolution of biofilm research

A

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

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13
Q

Differentiation in biofilms

A

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

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14
Q

Multicellular traits in biofilms

A

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

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15
Q

Communication (quorum sensing)

A

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

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16
Q

AHL mediated biofilm formation

A

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

17
Q

AI-2

A

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

18
Q

Quorum sensing blockers

A

Can this stop biofilm formation?
Eg cystic fibrosis

19
Q

Dispersal of biofilm cells and recolonisation

A

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

20
Q

Applications of biofilm knowledge

A

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

21
Q

Reversible and irreversible attachment

A

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

Wan der waals forces, repulsive electrostatic forces and polymer bridging

22
Q

10-20mm

A

Repulsive electrostatic interactions

23
Q

2-10nm

A

Repulsive and attractive electrostatic interactions

24
Q

0.5-2nm

A

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

25
Q

Attachment at long distances (5-20nm)

A

Van Der waals
Reversible binding
Little energy needed to remove bacteria eg spinning of flagellum

DLBO theory - applies to all particles in liquid

26
Q

Attachment at short distances (0.2-2nm)

A

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

27
Q

Polymers in combed in specific irreversible adhesion

A

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

28
Q

Two types of binding using surface structures for polymer bridging

A

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

29
Q

Key lock mediated adhesion

A

Pili or fimbriae
Afimbrial adhesion - attachment through receptors

30
Q

Fimbriae mediated binding

A

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

31
Q

Ecological advantages of Fimbriae

A

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

32
Q

Key lock binding often occurs on living surfaces because:

A

Epithelial cells expose lipids, proteins and mucus layers

These have receptor sites (carbohydrates, peptide sequences)

33
Q

FimH

A

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

Microbio & Biofilms (8 decks)

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