Résumé
The expansion of Pseudosuccinea columella snails worldwide has boosted Fasciola transmission. Most P. columella are susceptible to F. hepatica but a few field-occurring populations are resistant to the parasite in association with a potent immune response possibly based on gene-for-gene interactions. The microbiota plays a critical role in training the host’s immune system, while the immune system orchestrates the maintenance of key features of host-microbe symbiosis. Hence, we hypothesized that a distinct microbiome signature exists in resistant P. columella in relation to its genetic/phenotypic identity that is maintained across ecological contexts and that adds host fitness for resistance. The microbiome, the infection and the genetics of resistant and susceptible populations were characterized at G0 (field generation; occurring in sympatry or allopatry) and G2 (2nd lab-generation). Overall, the microbiome composition of resistant snails was site-specific but the microbiome of resistant differs from susceptible snails, even in sympatry. A clearer genotype-wise segregation was observed in lab-G2. Spatio-temporal shifts (G0-G2) reduced microbiome diversity, homogenizing variability and conserving population/phenotype identity. Dysbiosis after experimental exposure to F. hepatica was observed, following similar kinetics but still completely segregated phenotype wise. Parasite exposure also resulted in specific microbiota signatures that varied as infection/exposure progresses. An association of resistant snails with certain genera (Pirellula, Luteobacter, Roseomonas) and Phyla (Genmetimonadota, Halanaerobiaeota) was depicted. To answer if the microbiome has a significant effect on host resistance to F. hepatica infection in P. columella, experimental approaches of microbiome transfer from one phenotype to the other, in cross-combinations, are ongoing.