PhD defense: Salomé Gutiérrez-Ramos. Acoustic confinement of Escherichia coli: The impact on biofilm formation

PhD defense on October 18th, 2018, 2:30pm, at the PMMH meeting room (Sorbonne Université, Barre Cassan, Bât. A 1er Étage, 7 Quai Saint Bernard, 75005 Paris).

Acoustic confinement of Escherichia coli: The impact on biofilm formation

Brownian or self-propelled particles in aqueous suspensions can be trapped by acoustic fields generated by piezoelectric transducers usually at frequencies in the Megahertz. The obtained confinement allows the study of rich collective behaviours like clustering or spreading dynamics in microgravity-like conditions. The acoustic field induces the levitation of self-propelled particles and provides secondary lateral forces to capture them at nodal planes. Here, we give a step forward in the field of confined active matter, reporting levitation experiments of bacterial suspensions of Escherichia coli. Clustering of living bacteria is monitored as a function of time, where different behaviours are clearly distinguished. Upon the removal of the acoustic signal,motile bacteria rapidly spread, impelled by their own swimming. Short term trapping of diverse bacteria phenotypes results in irreversible bacteria entanglements and in the formation of free-floating biofilms-like structures.

Jury:

Harold Auradou (FAST, Université Paris–Saclay) Rapporteur
Philippe Marmottant (LiPhy, Université de Grenoble Alpes) Rapporteur
Nelly Henry (LJP, Sorbonne Université) Examinatrice
Sophie Ramananarivo (LadHyX, Ecole Polytechnique) Examinatrice
Jean-Luc Aider (PMMH, ESPCI Paris) Invité
Jesus Carlos Ruiz-Suárez (CINVESTAV Monterrey) Invité
Ramiro Godoy-Diana (PMMH, ESPCI Paris) Directeur de thèse

Synchronisation and pattern formation in fish swimming

Tetrafish2

Simple phalanx pattern leads to energy saving in cohesive fish schooling
I. Ashraf, H. Bradshaw, T. T. Ha, J. Halloy, R. Godoy-Diana, B. Thiria
PNAS 114 (36) 9599-9604 (2017)
[doi:10.1073/pnas.1706503114]PDF file

Synchronisation and collective swimming patterns in Hemigrammus bleheri
I. Ashraf, R. Godoy-Diana, J. Halloy, B. Collignon, B. Thiria
Journal of the Royal Society Interface 13 20160734 (2016)
[doi:10.1098/rsif.2016.0734] PDF file

The question of how individuals in a population organize when living in groups arises for systems as different as a swarm of microorganisms or a flock of seagulls. The different patterns for moving collectively involve a wide spectrum of reasons, such as evading predators or optimizing food prospection. Also, the schooling pattern has often been associated with an advantage in terms of energy consumption. We use a popular aquarium fish, the red nose tetra fish, Hemigrammus bleheri, which is known to swim in highly cohesive groups, to ana- lyze the schooling dynamics. In our experiments, fish swim in a shallow-water tunnel with controlled velocity, Continue reading “Synchronisation and pattern formation in fish swimming”