Microbiome affects adaptation of Drosophila melanogaster to high NaCl concentration

Symbiotic microbes affect a wide range of biological processes and possibly may contribute to the adaptation of higher organisms to environmental change. However, direct experimental evidence for such contribution is limited. We used two wild type laboratory strains of Drosophila melanogaster adapted to high NaCl concentration and two control strains reared on standard medium to assess the possible impact of symbiotic microbes on salt adaptation. We find that pre-inoculation of the high-salt food medium with homogenized flies from the salt-adapted strains enhances reproduction and shortens larval development time compared to pre-inoculation by homogenized flies from the control strains. The results are compatible with the idea that symbiotic microbes contribute to adaptation of D. melanogaster to high-salt medium. We also show that taxonomic composition of yeasts vectored by the flies differ between salt-adapted and control strains, implying the possible contribution of symbiotic yeasts to adaptation of flies to high NaCl concentrations. Evolutionary implications of such contribution are discussed.