Swimming-Induced Mechanoresponsive Material Stigmergy

Informations projet

SIMMS

N° de convention de subvention: 101029079

DOI

10.3030/101029079

Projet clôturé

Date de signature de la CE 7 Decembre 2021

Date de début 1 Decembre 2022

Date de fin 30 Novembre 2024

Financé au titre de

• EXCELLENT SCIENCE - Marie Skłodowska-Curie Actions

Coût total

€ 207 312,00

Contribution de l’UE

€ 207 312,00

Coordonné par

KOBENHAVNS UNIVERSITET
Denmark

Periodic Reporting for period 1 - SIMMS (Swimming-Induced Mechanoresponsive Material Stigmergy)

Période du rapport: 2022-12-01 au 2024-11-30

Résumé du contexte et des objectifs généraux du projet

At high densities, many organisms begin to exhibit collective motion, such as flocks of birds, schools of fish, and, on a microscopic scale, swimming microorganisms.
These microorganisms are ubiquitous, existing within humans, in soils, and in industrial environments, and they form remarkable patterns at sufficiently high densities.
The collective motion of these microorganisms is described as a "living liquid," which moves chaotically, often called bacterial turbulence, on a collective length and timescale.
Like a conventional liquid, the container or environment, e.g. a box or a pipe, influences the flow and dynamics of this living liquid.
However, many biological systems exist in soft, pliable environments where the living liquid can actively reshape its surroundings.
This interaction suggests a two-way relationship: the living liquid influences the environment, and the environment, in turn, affects the liquid's behavior.
SIMMS aimed to investigate these mutual interactions, as understanding these dynamics could lead to innovative applications, such as regulating bacterial activity to enhance bio-degradation, prevent contamination, and combat infections.
The project explored three initial environments: bacteria in porous media, bacterial colonies at soft interfaces, and bacteria in responsive gels.
Throughout the project, multiple instances of indirect coordination between bacteria and their material environments were observed, paving the way for exciting new research into multi-scale self-organized complexity in biological materials.

Travail effectué depuis le début du projet jusqu’à la fin de la période considérée dans le rapport et principaux résultats atteints jusqu’à présent

This project initially explored how bacteria-like swimmers move and interact in porous media, e.g. sand.
SIMMS findings revealed that bacterial turbulence enhances transport through porous media, with optimal conditions depending on the size and spacing of obstacles in the porous media
Additionally, SIMMS investigated how bacteria interact with mobile obstacles, showing that bacterial turbulence significantly enhances the movement of these objects when length-scales of the bacterial turbulence and obstacles were comparable.
These insights advance our understanding of bacterial dynamics and could inspire in the future applications in areas like filtration and bio-degradation.

Next, SIMMS focused on how bacterial colonies confined within soft environments respond to mechanical competition between species.
Bacterial competition for nutrients and space is critical in shaping biofilms. While previous studies emphasized chemical and motility traits, the research here uncovered that a simple mechanical feature—the cell's shape (aspect ratio)—can also play a dominant role.
The project showed through simulations in collaboration with experiments that elongated bacterial cells align collectively, forming structures called nematic arms. These arms mechanically connect the colony's core to its growing edges, enabling one species, the larger one, to out compete the other.
Our findings were confirmed using both particle-based and continuum simulations, providing a strong theoretical basis for understanding bacterial competition providing a possible pathway for anti-fouling methods through mechanical means rather than through chemicals.

Lastly, SIMMS aimed to explore how active particles, like swimming bacteria, interact with soft, connected tissues materials. Here, the project mostly investigated a colloidal gel as a toy-model for more complex connective tissue.
Initially, the mechanical response of colloidal gels under stress, using simulations across multiple scales to understand how these materials deform and fail were performed.
The findings showed that gels transition from a stable, stress-bearing state to a fluid-like state during failure, offering new insights into how soft materials reconfigure under pressure.
Next, SIMMS studied how active particles interact with these colloidal gels, revealing that the particles dynamically reorganize the gel's structure.
This restructuring creates denser regions while maintaining pathways for particle movement, enhancing transport and adaptability.
Using topological data analysis (TDA), SIMMS further uncovered how active particles reshape the gel's internal structure, improving its accessibility and mechanical properties.
These findings advance our understanding of active matter in soft environments, with applications in material science and biology.

Progrès au-delà de l’état des connaissances et impact potentiel prévu (y compris l’impact socio-économique et les conséquences sociétales plus larges du projet jusqu’à présent)

Throughout the project, multiple instances of indirect coordination between bacteria and their material environments were observed.
SIMMS was one of the first projects highlighting how material responsibility between bacteria and soft pliable environments is often overlooked.
The work here could be of tremendous importance to both collective dynamics and surrounding structures of swimming organisms.
Restructuring of responsive micro-environments by collective motion of bacteria represents a newly discovered complexity to biophysical problems and opens pathways for regulating bacteria dynamics to aid bio-degradation, hinder contamination and combat medical infections.

Swimmers produce collective dynamics, inducing deformations and, in turn, regulating swimmer dynamic