Authors

F Chevalier²; L V Carruthers¹; S Nordmeyer²; T Anderson²; W Le Clec'h²;  ¹ Institute of Infection, Immunity and Inflammation, University of Glasgow, UK;  ² Texas Biomedical Research Institute, United States

Discussion

The microbiome – the microorganism community found on or within an animal’s body – is increasingly recognized to shape many aspects of biology. The microbiome may influence carriage and transmission of pathogens by disease vectors such as mosquitoes. We previously sequenced the V4 variable region of the bacterial 16S ribosomal DNA from the hemolymph (blood) of Biomphalaria spp. snails revealing a diverse microbiome. We hypothesized that the snail microbiome may represent a critical, but unexplored intermediary in the snail-schistosome interaction as the parasite is in very close contact with organs and hemolymph during its development.

To understand the heterogeneity of the microbiome in different snail organs bathed by the hemolymph, we sampled 4 organs (ovotestis, liver, gut, and stomach), and the hemolymph from five snails from two different species (B. alexandrina and B. glabrata). We also crushed two whole snails of each species in liquid nitrogen and sampled the water in which the snails were living (environmental control). We then extracted the DNA from each sample and performed 16S sequencing on a MiSeq platform. We found significant differences in the microbiome composition from different snail organs and hemolymph. The highest microbial diversity is found in the hemolymph and the whole snails while the other organs showed more limited diversity. Sample type (organs and hemolymph), rather than snail species, is the main factor explaining the difference in microbial diversity, suggesting that specific organ environment shapes its microbiota. Furthermore, the physical distance between organs reflects the relative distance between organ microbiomes.

These results suggest that sampling hemolymph may be sufficient to capture most of the microbial diversity present in snails but sampling individual organs can provide a more complete description of the snail microbiome. Sampling microbiomes from whole snails provides a composite microbiome from several organs and tissues so may not be ideal.