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24 months position, open from April 2022 or as soon as possible thereafter.

How does mutualism with microbes emerge? How this process favored the appearance and evolutionary radiation of animal lineages whose nutrition is highly specialized? Why are these mutualistic systems not evolutionary stable? Through an innovative experimental approach using tick cell lines, we are looking for a highly motivated and talented post-doc to work on these fundamental questions.

Context:

Mutualism with microbes is one of the keys to the origins of complex life on Earth (Wernegreen, 2012; Bennett et al, 2015). In many cases, the host and its beneficial microbes merge into a single, coherent symbiotic entity so that these mutualistic relationships are considered stable associations over extremely long periods. Yet recent evidence of gains and losses of mutualistic symbionts suggests that the stability of beneficial mutualistic relationships is only apparent (Bennett et al, 2015; McCutcheon et al, 2019). However, the mechanisms favouring the extinction of ancestral, coevolved, symbionts and their ultimate replacement by foreign, less-coevolved, symbionts remain poorly understood.

In this context, our objective is to identify the evolutionary mechanisms that drive extinction and reborn of mutualistic interactions using ticks (Ixodida, Acari) as ideal biological models to address this question. Ticks host nutritional symbionts that are essential for their growth and survival, but the origin of these symbionts varies considerably between host species and substitution of beneficial symbionts can occur (Gottlieb et al, 2015; Duron et al, 2018; Guizzo et al, 2017; Duron et al, 2017; Binetruy et al, 2020).
Members of our consortium have demonstrated that Francisella sp. (Gamma-proteobacteria: Thiotrichales: Francisellaceae) is an obligatory symbiont for ticks by providing them with B vitamins (Duron et al, 2018). Surprisingly, from a large screening, most tick species harbour a different intracellular symbiont, Coxiella sp. (Gamma-proteobacteria: Legionellales: Coxiellaceae), which is also able to synthetize B vitamins (Duron et al, 2017; Binetruy et al, 2020). Overall, these works show repeated replacements of Coxiella by Francisella across the tick phylogeny (Duron et al, 2017; Binetruy et al, 2020) but the factors favouring one nutritional mutualist, over another, are not yet understood.

Post-doc project:

The position is associated with the ANR-funded collaborative project MICROM “Microbial competition in mutualistic interactions with ticks”. The MICROM consortium, led by Olivier Duron, involves three teams (O. Duron MIVEGEC, Montpellier, F. Vavre LBBE, Lyon and D. Bouchon EBI, Poitiers) with excellent expertise in the field of endosymbiosis.
MICROM aims at deciphering the competition between Francisella and Coxiella symbionts using different approaches from genomics, transcriptomics, in vivo and in vitro imaging. The recruited post-doc will participate in this innovative program with a particular focus on in vitro experiments assessing the competitive abilities of the two beneficial symbionts. The post-doc will be responsible for monitoring tick cell lines, performing infection and co-infection and characterising the cellular phenotypes. Methods include RT-qPCR, dual-RNAseq, FISH combined with electron microscopy.

Teams, lab and location:

The post-doc will be part of the Ecology, Evolution & Symbiosis team of the EBI laboratory in Poitiers, which has a long experience in research on symbiosis. The post-doc will have access to the funding and infrastructures needed for this project, in a stimulating scientific environment. Regular exchanges and mobility are planned with the various project partners as well as with external collaborators such as the Tick Cell BioBank in Liverpool.

Remuneration will be between € 2,663 and € 3,789 gross per month depending on experience.

Relevant expertise:

We are looking for an autonomous and highly motivated candidate with a genuine interest in symbiosis research with expertise in the following areas:
 Cell culture
 Molecular biology
 Imaging approaches, cellular biology, histology. Experience in electron microscopy is a plus.
 Interested in acquiring expertise in experimentation with arthropods: care, injection, dissection
 Expertise in genomics and bioinformatics is a plus

Application:

The application form should be submitted on the CNRS job portal by following this link: https://bit.ly/3LKQBsk 
Please send also your application:
CV including publication list
Two references (including email addresses and/or recommendation letter)
Letter of motivation
Concise summary of previous research activities

to: Didier Bouchon (didier.bouchon@univ-poitiers.fr)