Role of the microbiome of the schistosome snail host - 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.