PhD, University of Poitiers (France), 2013
- Supervisors : Didier Bouchon, Monique Johnson
Host-associated Microbiota in Armadillidium vulgare: Feminizing Wolbachia and other major players
Terrestrial isopods represent an excellent model system for multipartite animal-bacteria symbioses due to their well-characterized association with the endosymbiotic reproductive parasite Wolbachia. To date, three different feminizing Wolbachia strains have been identified in Armadillidium vulgare, presumably representing different co-evolutionary histories. The aim of this PhD was to get a more complete picture of the terrestrial isopod microbiome and the role of Wolbachia within the bacterial community. In order to achieve this, the microbiota of A. vulgare was characterized on multiple levels: (i) In field populations and controlled laboratory lineages, (ii) in different host tissues, and (iii) depending on the Wolbachia infection status. Technically, this was achieved using a combination of quantitative PCR, genetic fingerprinting via Temperature Gradient Gel Electrophoresis (TGGE) and 454 amplicon pyrosequencing of the 16S rRNA gene. This integrative approach allowed us to identify the major factors shaping the microbiota associated with A. vulgare. In addition, the complete genome sequence of another highly abundant facultative symbiont, Candidatus Hepatoplasma crinochetorum (Mollicutes), was obtained. In combination with available data from the host transcriptome, this new genome enabled a preliminary investigation of functional interactions between A. vulgare and this relatively unknown symbiont. This thesis opens new perspectives for the study of terrestrial isopod-bacteria symbioses.
1. Dittmer J, Koehler A, Richard F-J, Poulin R, Sicard M (2011). Variation of parasite load and immune parameters in two species of New Zealand shore crabs. Parasitol Res 109: 759-767
2. Dittmer J, Lesobre J, Raimond R, Zimmer M, Bouchon D (2012). Influence of Changing Plant Food Sources on the Gut Microbiota of Saltmarsh Detritivores. Microb Ecol 64: 814-825
3. Leclercq S, Dittmer J, Bouchon D, Cordaux, R (2014). Phylogenomics of ‘Candidatus Hepatoplasma crinochetorum’, a lineage of Mollicutes associated with non-insect arthropods. Genome Biol Evol (accepted)
4. Dittmer J, Beltran S, Lesobre J, Raimond M, Johnson M, Bouchon D. Host tissues as microhabitats for Wolbachia and quantitative insights into the bacterial community in terrestrial isopods. Mol Ecol (In review)