The gut microbiota is an important source of metabolic innovations for animal hosts, and is increasingly considered as a key factor that may drive adaptation to the fast and drastic environmental changes imposed by human activities and global warming. We recently showed that in the freshwater crustacean Daphnia magna, genetic and plastic variation in the gut microbiota mediate tolerance to toxic cyanobacteria, pointing to the gut microbiota as a driver of adaptation and acclimatization to cyanobacterial harmful algal blooms in zooplankton. Our results further revealed that host genotype contributes to shape the structure and the functionality of the gut microbiota in this species.

The aim of the present project is to unravel the functional mechanisms underlying the establishment of these mutualistic symbionts in the Daphnia gut, especially the role of host immunity in structuring the gut microbiota. We will focus on a candidate gene recently identified in the Daphnia genome, which encodes a peptide sequence (called “daphniamacine”) similar to an antimicrobial peptide structuring the gut microbiota in leeches. The objectives of the study will be to determine : (1) whether the microbiota induces the expression of the daphniamacin in the Daphnia guts, by comparing the gene expression in germ-free versus conventional Daphnia, (2) whether the assembly of “tolerant” and susceptible” microbiota profiles is governed by the daphniamacin, by comparing the gene expression in tolerant and susceptible clones, and (3) whether the sequence, or the expression, of the gene evolved over time, by comparing old, resurrected*, populations (dormant in sediment, up to 40 year-old) to actual populations.

* Daphnia produce dormant eggs that can survive in sediments for long periods of time, and that can be revived in the laboratory

Work, technics and fields of competences:
– essentially molecular biology: PCR, cloning, sequence analyses
– culture of Daphnia and dissection of the gut

All the technics have already been optimized, the candidate will have to be meticulous because of the small amounts of materials and the methods used

Masters in molecular biology, ecology, ecophysiology, genetics, microbiology

English spoken required

For more informations please do not hesitate to contact the supervisors.

Supervisors: Aurélie Tasiemski, Emilie Macke and Ellen Decaestecker

Sites : Université de Lille1, CNRS UMR8198, unité EEP, bat SN2, 59655 Villeneuve d’Ascq cedex and Laboratory Aquatic Biology, KU Leuven (Kulak), Dept of Biology, E. Sabbelaan 53, BE-8500, Courtrai, Belgique

Phones : 03 20 33 59 57 (AT); +32 56 24 64 09 (EM) ; +32 56 24 60 59 (ED)

Mails : [email protected]; [email protected]

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