Modelling of surfactant-driven front instabilities in spreading bacterial colonies.

  title={Modelling of surfactant-driven front instabilities in spreading bacterial colonies.},
  author={Sarah Trinschek and Karin John and Uwe Thiele},
  journal={Soft matter},
  volume={14 22},
The spreading of bacterial colonies at solid-air interfaces is determined by the physico-chemical properties of the involved interfaces. The production of surfactant molecules by bacteria is a widespread strategy that allows the colony to efficiently expand over the substrate. On the one hand, surfactant molecules lower the surface tension of the colony, effectively increasing the wettability of the substrate, which facilitates spreading. On the other hand, gradients in the surface… 

Figures from this paper

Thin-film modelling of complex fluids and bacterial colonies
This thesis develops and analyse simple models to clarify the role of passive physico-chemical forces and processes - such as osmosis, surface tension effects and wettability - in the spreading of bacterial colonies at solid-air interfaces and presents a phenomenologically derived model for active polar films.
An expanding bacterial colony forms a depletion zone with growing droplets.
This study reports the occurrence and spread of a depletion zone within an expanded colony, where the bacteria laden film becomes thinner, and explains the observed properties based on considerations of bacterial growth and secretion, osmotic swelling, fluid volume expansion, interfacial fluid dynamics involving Marangoni and capillary flows, and cell-cell cohesion.
A multiphase theory for spreading microbial swarms and films
A generalized two-phase thin-film model is developed that couples bacterial growth, extracellular matrix swelling, fluid flow, and nutrient transport to describe the expansion of both highly motile bacterial swarms, and sessile bacterial biofilms, and demonstrates how the physics of flow and transport in slender geometries serve to constrain biological organization in microbial communities.
An expanding bacterial colony forms a depletion zone with growing droplets
A model is proposed to account for the observed properties of the expansion of Pseudomonas aeruginosa on an agar gel surface, taking into consideration bacterial growth and secretion, osmotic swelling, fluid volume expansion, cell-cell interaction, and interfacial fluid dynamics involving Marangoni flow.
A thin-film extensional flow model for biofilm expansion by sliding motility
An extensional flow model for biofilm expansion by sliding motility is derived, and it is shown that the model can explain the ridge formation observed in some biofilms, especially true if surface tension is low.
A Thin-Film Lubrication Model for Biofilm Expansion Under Strong Adhesion
A thin-film model for microbial biofilm growth on a solid substratum to which it adheres strongly is developed and it is revealed that expansion speed depends on cell proliferation, nutrient availability, cell–cell adhesion on the upper surface, and slip on the biofilm–substratum interface.
Active modulation of surfactant-driven flow instabilities by swarming bacteria.
A more complete model for bacterial pattern formation which accounts for the effect of bacterial sensing and decision making by coupling active bacterial motility to the passive fluid dynamics is presented.
Fingering instability of active nematic droplets
  • Ricard Alert
  • Physics
    Journal of Physics A: Mathematical and Theoretical
  • 2022
From the mitotic spindle up to tissues and biofilms, many biological systems behave as active droplets, which often break symmetry and change shape spontaneously. Here, I show that active nematic
Use of Alternative Gelling Agents Reveals the Role of Rhamnolipids in Pseudomonas aeruginosa Surface Motility
Assessment of surface motility capabilities of the prototypical strain PA14 on semi-solid media solidified with alternative gelling agents, gellan gum and carrageenan found that rhamnolipids do not have such a crucial role in achieving surface colonization of non-agar plates, suggesting a strong dependence on the physical properties of the tested surface.
Physical factors contributing to regulation of bacterial surface motility
These findings illuminate the physical structure of surface-motile groups and demonstrate that physical properties, like cellular packing fraction and flow, regulate motion from the scale of individual cells up to length scales of centimeters.


From a thin film model for passive suspensions towards the description of osmotic biofilm spreading
A model which de- scribes the biofilm evolution and the advancing biofilm edge for this spreading mechanism is presented, based on a gradient dynamics formulation for thin films of biologically passive liquid mixtures and suspensions, supplemented by bioactive processes which play a decisive role in the osmotic spreading of biofilms.
Continuous versus Arrested Spreading of Biofilms at Solid-Gas Interfaces: The Role of Surface Forces.
It is shown that surface forces determine whether a biofilm can expand laterally over a substrate and experimental evidence for the existence of a transition between continuous and arrested spreading for Bacillus subtilis biofilms is provided.
Bacillus subtilis spreads by surfing on waves of surfactant
Experiments and a mathematical model demonstrate how the differential accumulation rates induced by the geometry of the bacterial film give rise to surfactant waves, which increases with increasing biofilm viscosity.
Water surface tension modulates the swarming mechanics of Bacillus subtilis
Light is shed on the role of water surface tension in regulating B. subtilis swarming, and insight is provided into the mechanisms underlying swarming initiation and tendril formation.
The spreading and stability of a surfactant-laden drop on a prewetted substrate
We consider a viscous drop, loaded with an insoluble surfactant, spreading over a flat plane that is covered initially with a thin liquid film. Lubrication theory allows the flow to be modelled using
Surface tension gradient control of bacterial swarming in colonies of Pseudomonas aeruginosa
This work shows how the bacterial swarming can be caused by a surface tension driven flow and demonstrates that surface tension gradient control can even be the dominant mechanism that drives swarming.
Fingering phenomena created by a soluble surfactant deposition on a thin liquid film
A striking fingering instability accompanies surfactant droplet deposition upon thin films. The fingers apparently emerge from the droplet and are preceded by a circular rim of thickened fluid. In
The development of transient fingering patterns during the spreading of surfactant coated films
The spontaneous spreading of an insoluble surfactant monolayer on a thin liquid film produces a complex waveform whose time variant shape is strongly influenced by the surface shear stress. This
Thin-film modelling of biofilm growth and quorum sensing
Biofilms are slimy films of bacteria that typically grow on solid surfaces with a fluid interface. Two mathematical models for nutrient-dependent, early-stage biofilm growth and quorum sensing (QS)