Cohesion and Inversion in C. flexa, the Closest Animal Relative (M/F)

4 Apr 2024
Job Information

Organisation/Company

CNRS

Department

Institut Jean le Rond d'Alembert

Research Field

Engineering » Materials engineering
Physics » Acoustics

Researcher Profile

First Stage Researcher (R1)

Country

France

Application Deadline

24 Apr 2024 - 23:59 (UTC)

Type of Contract

Temporary

Job Status

Full-time

Hours Per Week

35

Offer Starting Date

1 Oct 2024

Is the job funded through the EU Research Framework Programme?

Not funded by an EU programme

Is the Job related to staff position within a Research Infrastructure?

No

Offer Description

∂'Alembert Institute is a research laboratory whose mission is to expand the field of knowledge in all areas of Mechanics, Acoustics, and Energetics. ∂'Alembert is a Joint Research Unit of the Faculty of Science and Engineering at Sorbonne University (formerly UPMC - Pierre and Marie Curie University) and the CNRS (UMR7190), also supported by the Ministry of Culture. Bringing together nearly one hundred and seventy individuals, including approximately eighty permanent staff, around seventy doctoral students, and about twenty temporary staff, such as teaching assistants, postdoctoral researchers, or others, it constitutes the largest research laboratory in the Île-de-France region in its field of activity.

1) Scientific Context:
Multicellularity has emerged multiple times throughout evolution in marine environments. Specifically, choanoflagellates are unicellular microorganisms capable of organizing into colonies. They are also the closest relatives to animals, and their study sheds light on the evolution towards multicellularity: humanity finds the narrative of its origins among choanoflagellates. Choanoeca flexa is a species of choanoflagellate discovered only in 2019, and its mechanical characterization remains to be done. Like all choanoflagellates, the cells of C. flexa have a flagellum that creates propulsive flows, and a collar that filters water and captures bacteria to feed the cell. Some species of choanoflagellates form rosette colonies: the cells are attached by an extracellular matrix, with flagella pointing outward in all directions. C. flexa also forms colonies, but adhesion occurs at the collar level, without an extracellular matrix. The cells are organized in a monolayer with all flagella on the same side. This cell layer has a natural curvature imposed by the opening angle of the collars. In the "relaxed" configuration, the flagella are inside the half-sphere and generate a flow that allows cells to feed, while in the "active" configuration, the flagella are outside the half-sphere and the colony swims. Colonies of C. flexa have the remarkable property of inverting: the entire colony opens and closes in a sort of reversible gastrulation.

2) Thesis Objectives:
C. flexa was discovered in puddles on the coast of Curaçao: these choanoflagellates evolve in a transient environment, fueled by waves and subjected to evaporation, where they are threatened by numerous predators. The transition to multicellularity has multiple benefits, such as more efficient feeding, better defense, and reducing the energy cost of movement. What are the advantages of multicellularity in C. flexa?
The experimental thesis will be organized along three axes: first, how do colonies form? In particular, we will model the adhesion force between cells, which do not secrete an extracellular matrix to maintain the colony. Then, how do colonies invert? We will study the force provided by a cell when opening its collar, and explore the hydrodynamic role of the flagella. Finally, what is the inversion dynamics? We will quantify the environmental factors that trigger inversion and model the stability of the "active" configuration before it relaxes. These results will demonstrate the evolutionary advantage of forming colonies.

3) Skills/Knowledge:
- Strong competence in hydrodynamics
- Strong competence in biophysics
- Experience with handling microorganisms
- Fluent in English

Requirements

Research Field

Engineering

Education Level

Master Degree or equivalent

Research Field

Physics

Education Level

Master Degree or equivalent

Languages

FRENCH

Level

Basic

Research Field

Engineering » Materials engineering

Years of Research Experience

None

Research Field

Physics » Acoustics

Years of Research Experience

None

Additional Information

Website for additional job details

https://emploi.cnrs.fr/Offres/Doctorant/UMR7190-JULPIE-001/Default.aspx

Work Location(s)

Number of offers available

1

Company/Institute

Institut Jean le Rond d'Alembert

Country

France

City

PARIS 05

Geofield

Where to apply

Website

https://emploi.cnrs.fr/Candidat/Offre/UMR7190-JULPIE-001/Candidater.aspx

Contact

City

PARIS 05

Website

http://www.dalembert.upmc.fr

STATUS: EXPIRED