2019-5-Offer for a Thesis Allowance - Subject: Influence of the environmental conditions on the methylation rates and source of Hg speciesin microorganisms

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Offer for a Thesis AllowanceSubject: Influence of the environmental conditions on the methylation rates and source of Hg speciesin microorganisms

Thesis subject

Mercury (Hg) is a persistent pollutantin the environment, highly volatile and able to be converted into highly toxic methylmercury (MeHg). MeHg is a serious threat as it is a neurotoxic compound, which is bioaccumulated and bioamplified in food webs. Microorganisms play a central role in MeHg conversion, either directly by controlling Hg methylation and MeHg degradationeither indirectly. Although hgcAand hgcAgenes have been identified as necessary for Hg methylation, today, the methylation process cannot be fully explained. Together with environmental factors, other genetic determinisms are suspected to be involvedin mercury methylation. To date, little is known about the cellular and environmental mechanisms favouring MeHg production, and Hg methylation processes are far from being deciphered.

Our team at IPREM lab aims to characterize Hg methylation at cellular level, from Hg recognition by the cell to Hg export, including methylation steps. We intend to decipher the role of Hg cell trafficking in the Hg methylation process in two Sulfate Reducing Bacteria (SRB) model strains, Pseudodesulfovibrio hydrargyriBerOc1, able to methylate Hg and demethylate MeHg and Desulfovibrio alaskensisG20, able to exclusively demethylate MeHg. The objective of the thesis is to investigate the molecular aspects of mercury biotransformations, including studies on the biomolecular speciation and the localization of Hg transformations at the subcellular level by combining chemical and physical analytical methods.

The proposed PhD is part ofthe project ‘GO-BEAM’ (Go inside a bacterial cell methylating Mercury) funded by E2S-UPPAfrom 2018 to 2021. GO-BEAM, selected as a ‘Key Scientific Challenges E2S-UPPA’ (http://e2s-uppa.eu/en/index.html ) is a collaborative and transdisciplinary project involving genetic microbiology, analytical chemistry, imaging and spectroscopy. The objective of the project is to improve the understandingof the Hg methylation/demethylayion processes at the cell level. 2 PhD and 1 Post-Doctorate are funded for the GO-BEAM project: PhD1 on analytical and imaging(the present proposition), PhD2 on genetic microbiology and physiological studies and the Post-Doc on both imaging and spectroscopy. Scientific team: MP Isaure, M Goñi-Urriza, M Monperrus, B Khalfaoui-Hassani, R Guyoneaud, C. Gassie,2 PhD students, 1 post-doc

mercury methylation, sulfate-reducing bacteria, Hg speciation, mass spectrometry, transmission electron microscopy



The PhD student will be in charge of the bacterial cultures in various conditions and various ligands.

He/she will have to model Hg speciation using (bio)geochemical software (VMinteq).

He/she will perform incubations using isotopically enriched mercury species followed by GC-ICPMS analysis to establish simultaneously methylation and demethylation rates and quantities of net methyl mercury production rates. He/she will be strongly involved in the identification of thiols ligands by HPLC-ESI-MS/MS.

He/she will also set experiments with labelled stable S isotopes to track the source of S in Hg-S-containingcompounds, particularly using nanoSIMS.

In collaboration with the BIC in Bordeaux, he/she will also implement transmission electron microscopy (particularly HRSTEM)to correlate ultrastructures (membranes, periplasm, cytoplasm) and nanoSIMS images.-

He/she will work with another PhD studentinvolved in microbial genetics and physiologyand a post-doc, involved in X-ray imaging and X-ray Absorption Spectroscopytechniques. The role of candidate genes in Hg methylation will be assessed through gene deletion and complementation in D. hydrargyriBerOc1. Applying X-ray imaging on the wild type and mutants, theHg methylation potentials and localizationwill be characterized in order to decipher the role of the genes on Hg pathways.

The phD student will also participate to teaching activities at the undergraduate level (96h/3 years).


Working conditions

Hosting laboratory: IPREM, Pau, France
Environment and Microbiology, Analytical and bioinorganic chemistry

Host laboratory profile: Analytical chemistry, mass spectrometry, X-Ray Absorption Spectroscopy, Imaging, Microbiology, Physiology, Genetics, MicrobialEcology, Environmental Microbiology

Localisation address: Université de Pau et des Pays de l’Adour, campus of Pau, Pyrénées-Atlantiques, France

PhD supervisor: Mathilde Monperrus
PhD co-supervisor: Marie-Pierre Isaure
In collaboration with Marisol Goñi-Urriza

Starting date: October 2019

Length: 3 years

Employer: Université de Pau et des Pays de l’Adour (UPPA)
Funding: E2S UPPA

Gross monthly salary: 1878 €
(UPPA doctoral contract, according to E2S UPPA project, including 96h of teaching during the three years)


Required skills and competences


The candidate should have a strong predilection for laboratory work.
The ideal candidate has a master degree in analytical chemistry or environmental chemistry.
He/She is rigorous, highly motivated and able to work autonomously.

Fluency in English is mandatory, French would be a plus.


Application - Evaluation criteria

The selection process includes two steps.

1st step:
- Evaluation of the applicants’ CV
- Selected candidates will be contacted by mail before June 26th.
The candidates selected after this first step, will then be interviewed.

2nd step:
Candidates will have 5 min to present their CV, 5 min to present their Master 2 thesis and 5min to present the phD subject.
This presentation will be followed by questions and discussion.

Application files will be evaluated based on the following criteria:

  • Candidate's motivation, scientific maturity and curiosity
  • Candidate's iknowledge
  • Grades and ranking during both your undergraduate studies and your Master degree, steadiness in your academic background
  • English language proficiency
  • Oral and written communication skills
  • Candidate’s ability to present her/his work and results
  • Professional experience or internship(s) in laboratory or other; any research work already carried out (reports, publications).


Application file composition and submission deadline

Application will include (in a single pdf file):

  • CV
  • Cover letter detailing the candidate's motivations
  • Candidate's undergraduate and Master grade transcripts and ranking
  • 2 Reference letters
  • Contact details of at least two people, from you work environment, who can be contacted for further reference

Applications must be sent to both of the following email addresses with the title “Doctoral application”: 
mathilde.monperrus @ univ-pau.fr
marie-pierre.isaure @ univ-pau.fr

For more details, please visit our websites: http://e2s-uppa.eu/en/index.html

Submission deadline : June 28th, 2019