Microbial communication Flashcards

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1
Q

what factors were the cause of the accumulation of so much biofilm in the Walkerton water system?

A
  • available water (moisture)
  • nutrients ( concrete pipes)
  • surface
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2
Q

using what you know about regulation of the Iac operon, and what you know about quorum sensing. make a diagram suggesting a method for regulation of an operon regulated by quorum sensing

A
  • inducible operon
  • concentration within environment regulates gene expression
  • regulators must interact with the components produced by cell
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3
Q

why do we study communication within a biofilm?

A
  • to understand

- inhibit biofilm growth by interrupting communication

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4
Q

natural competence

A

uptake of DNA found in environment

  • increase possibility for horizontal gene transfers
  • uptake for a source of protein
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5
Q

are humans prone to a form of unknown signalling similar to quorum sensing (i.e., a response generated due to our environment)?

A
  • pheromones :
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6
Q

bacterial pheromones

A

-all lipid and tend to be gram -

-

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7
Q

what is the function of luxR dimer

A

-it is an enhancer for the operon and allows RNA pol to bind (transcription) and in turn increase AHL productions and compounds leading to luminescence

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8
Q

Quorum Sensing

A

The regulation of gene expression in response to fluctuations in cell population density

Produce and release signal molecules into the environment called autoinducers

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9
Q

Pheromones

A

chemicals capable of acting outside the body of the secreting individual to impact the behaviour of the receiving individual. It is usually the case that we are not aware of the pheromone, it simply triggers a response

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10
Q

Vibrio fischeri (squid)

A
  • lux operon ( Intra-species) vibrio fischeri inside squids
    1. ) low levels of cell density and AHL results in no glow.
    2. ) increased level of cells and therefor increased AHL levels
    3. ) AHL levels high enough for dimer formation
    4. ) dimers will activate lux promoter and in turn transcribe +translates operon and proteins
    5. ) translated proteins create luminescence.
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11
Q

Rhizobium bac Infection (Root Hair)

A
  • Inter-kingdom (mutualistic relationship )
    1. Plant secretes flavonoids and attract Rhizobium bac
    2. bac create Biofilm cap
    3. Infection of thread (bac proliferation after nod gene expression)–> actin depolymerisation
    4. infection grows into root cortex
    5. infected threads release bac cells –> bacteroids (no cell wall at this point) into root cells
    6. Bacterial cytokinins lead to nodule development + plant cortical cells to divide
    7. plant supplies nutrients and O2 for bacteroids
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12
Q

Agrobacterium tumifaciens

A
  • soil borne plant pathogen
  • cause infectious crown gall disease
  • genes for infection are vir genes on Ti plasmid ( infectious viral DNA)
    1. ) virus enters host via wounds ( virA and virG attracted by acetosyringione)
    2. ) DNA incorporated and leads to auxin and cytokinin and opines productions
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13
Q

Auxins

A

– major role in coordination of many growth and behavioral processes in the plant’s life cycle and are essential for plant body development

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14
Q

Cytokinin

A

plant growth regulators

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15
Q

Opines

A

food source for bac specific to Agrobacterium so it has a selective advantage

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16
Q

A.tumifaciens maintain is plasmid during plant infections (quorum sensing)

A
  1. tra genes transfer Ti plasmid into bac (if it is lost)
  2. Tra/Tral is regualred by quorum sensing
  3. opines inhibit AccR –> transcription
  4. TraR produced only if opines around
  5. TraR recognize AHL + activate conjugation
17
Q

Inter-species cross talk

A
  • demonstration of cross-talk b/n rhizosphere bac
  • -> rhizosphere produce three pigmented antibiotics/phenazines
  • phenazine prodcution is reg. by quorum sensing
  • phenazine production is reg by PhzR/PhzI systems
  • -> I procudes AHL and R is a transcriptional reg.
18
Q

Positive Crosstalk

A
  • mutant bac regain phenazone production ability via AHL signals
19
Q

Negative Crosstalk

A
  • bac inhibit wild type bac to produce phenzaine production via diffusible signals
20
Q

Gram positive bac

A
  • do not have classical AHL mediated quorum
  • use gamma-butyrolactones to regulate genes ( resemble AHL somewhat)
  • use small peptides and act by de-repressing gene expression
  • -> respond Al-2
  • two component sensing system+ Autoinducidble peptide= three component system
21
Q

Two component system

A
  1. sensor protein (within cell membrane and senses changes in external envir.) –> communicates with RR (via phosphorylation-dephosphorylation reactions)
  2. response-reg (RR) (regulate expression of key genes to respond to external stimulus)
22
Q

Staphylococcus aureus

A
  • three component system

- positive and negative regulation

23
Q

Emergent phenomena within Biofilm

A
  • bac in communities use to enhance their survival (and their community)
  • behavior at a larger scale arises from the detailed structure
  • exterio cells are exposed first to chemical and antibiotic attacks + first exposed to nutrients
  • periphery growth is limited so nutrients can be used for the inner cells as well
  • keeping the inner cells alive and well ther biofilm as a whole will better survive an antibiotic treatment.