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Generic modelling of cooperative growth patterns in bacterial colonies Eshel Ben-Jacob et al. Letters to Nature, Mar 1994 Introduction/ Growth model Bacteria aggregate to random walkers within an envelope movement along the gradient of

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Generic modelling of cooperative growth patterns in bacterial colonies

Eshel Ben-Jacob et al. Letters to Nature, Mar 1994

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Introduction/ Growth model

  • Bacteria aggregate to random walkers within an envelope

movement along the gradient of nutrient concentration

  • Cooperative behavior to overcome unfavourable environmental

conditionen

Communication by means of chemotactic feedback

  • Growth pattern dependent on environment

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Experimental Setup

  • Bacillus subtilis strain 168 : initial value

~ 105

  • Nutrient: Peptone
  • Substrat: Agar

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5 g l-1

Growth pattern under variable conditionen

Decreasing peptone concentration (5– 0.25 g l-1 )

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Decreasing peptone concentration (5– 0.25 g l-1 )

5 g l-1 2 g l-1

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Decreasing peptone concentration (5– 0.25 g l-1 )

5 g l-1 2 g l-1 0.5 g l-1

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Decreasing peptone concentration (5– 0.25 g l-1 )

5 g l-1 2 g l-1 0.5 g l-1 0.25 g l-1

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Bacterial movement

  • Random-like movement within a defined

envelope

  • Propagation of envelope because of

collective movement

  • (f) presumably formed by excretion of

chemicals and/or by fluid drawn from agar

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Generic features of the bacterial growth model

1) Diffusion of nutrients

Consumption of food by walkers

2) Movement of bacteria

Location (ri) and internal Energy (Wi) determine the activity

3) Reproduction and sporulation

Reproduce if Wi~ threshold, sporulate if Wi ~ 0

4) Local communication

Envelope segments move after being hit Nc times

  • –

– e – loss rate of internal energy

  • ri – location, cr – fixed rate of nutrient consumption

–

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The communicating walkers model

Agar concentration (substrate) Peptone concentration (nutrient)

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How to achieve dense patterns at low peptone concentrations ?

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≠

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How to achieve dense patterns at low peptone concentrations ?

  • Chemotaxis!
  • Add chemotactic communication
  • –

–

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Stationary walkers: production of communication chemical at fixed rate sr Active walkers: consumption of communication chemical at a fixed rate cs

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Effect of Chemotaxis signaling on communicatin walkers model

P = 10 g l-1 , Nc =40 Movement changes from pure random-walk (any direction is equiprobable) à a walk along the gradient of communication.

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Excursus

Morphotypes of bacterial colonies

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Morphotypes of bacterial colonies

V(ortex)-Morphotype B(ranching)-Morphotype C(hiral) -Morphotype

result of cooperative behaviour

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Morphotype Transitions

Grows on hard substrates (higher density of bacteria)

B morphotype

Grows on softer substrates

C morphotype

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Morphotype Transitions

  • B-cells on soft agar à

morphotype transition and growth bursts of C-cells occurs (after ~ 48hrs)

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Thank you for your attention!

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Sources

  • http://rocs.hu-

berlin.de/complexsys2018/pdf/seminarpapers/eshel.pdf

  • https://pdfs.semanticscholar.org/dbfe/13260289e4ab91a737ec9ff8a

af90569f697.pdf

  • https://www.indiamart.com/proddetail/bacillus-subtilis-

7645289830.html

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