Role of the microbiome of the schistosome snail host

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PROJECT SUMMARY The microbiome – the community of microorganisms that inhabit both the human body and that of multiple other animal phyla – is increasingly recognized to play an important role in many aspects of biology and as a key determinant of health and disease. In invertebrates, symbiotic bacteria are involved in synthesizing essential aminoacids or vitamins, in digesting cellulose, in protection against parasites, in feminization and parthenogenesis, and even in speciation. In insect vectors, there are multiple examples of interactions between resident microbiomes and parasites: the sandfly gut microbiome mediates Leishmania transmission, Wolbachia bacteria can disrupt malaria transmission in mosquitoes, while the microbiome of both reduviid bugs and tsetse flies mediates trypanosome infection. Our goal is to study the microbiome of the freshwater snail Biomphalaria, vector of schistosomiasis: six lines of evidence suggest a possible role for the microbiome in the Biomphalaria - Schistosoma mansoni interaction: (i) the snail hemolymph (blood), to which sporocyst stage schistosomes are continuously exposed, harbors a diverse microbiome, (ii) this microbiome is differentiated from other organ microbiomes and shows the greatest microbial diversity within snails, (iii) different laboratory snail populations have a distinctive microbiome composition, (iv) co-culture of different snail populations results in rapid change in microbiome composition, (v) snail genotypes from a single population that are resistant or sensitive to schistosome infection have distinctive microbiomes and (vi) schistosome infection results in altered microbiome composition. In specific aim 1 we will directly test the impact of microbiome on snail host development and schistosome parasite susceptibility. This will be done by generating germ-free snails, just as germ-free mice have been used to understand the direct role of the microbiome in obesity. Microbiomes are dynamic and may vary in composition and abundance due to environmental factors. These microbiome modifications can even lead to host health and fitness alterations. Specific aim 2 will focus on the impact of microbiome modification on snail host fitness using long term co-culture (or common garden) of snail populations carrying distinctive microbiomes. We will characterize sampled microbiomes using next generation sequencing of the 16S ribosomal DNA. This project will (i) provide fundamental information about microbiome dynamics and composition, (ii) determine the role of the microbiome in the snail-schistosome interactions and snail ftiness, and (iii) has strong potential to reveal new aspects of the snail-microbiome-parasite interaction that can be targeted by novel interventions.