There is widespread interkingdom signalling between insects and microbes. For example, microbes found in floral nectar may modify its nutritional composition and produce odorants that alter the floral odor bouquet which may attract insect pollinators. Mosquitoes consume nectar and can pollinate flowers. We identified microbes isolated from nectar of common tansy, Tanacetum vulgare , identified the microbial odorants, and tested their effect on attracting the common house mosquito, Culex pipiens . Results We collected 19 microbial isolates from T. vulgare nectar, representing at least 12 different taxa which we identified with 16S or 26S rDNA sequencing as well as by biochemical and physiological tests. Three microorganisms, Lachancea thermotolerans, Micrococcus lactis , Micrococcus luteus , were grown on culture medium and tested in bioassays. L. thermotolerans grown on nectar, malt extract agar, or in synthetic nectar broth significantly attracted C. pipiens females. The odorant profile produced by L. thermotolerans varied depending on the composition of the culture medium used. Surprisingly, all three microbes grown separately, but presented concurrently, attracted fewer C. pipiens females than L. thermotolerans by itself. Conclusions Floral nectar of T. vulgare contains various microbes whose odorants contribute to the odor profile of inflorescences. In addition, one of the microbes, the yeast L. thermotolerans, produced odorants that attract Cx. pipiens females. As the odor profile of L. thermotolerans varied with the composition of the culture medium, we hypothesize that microbe odorants inform nectar-foraging mosquitoes about the availability of certain macronutrients which, in turn, affect foraging decisions by mosquitoes.

AbstractThere is widespread interkingdom signalling between insects and microbes. For example, microbes found in floral nectar may modify its nutritional composition and produce odorants that alter the floral odor bouquet which may attract insect pollinators. Mosquitoes consume nectar and can pollinate flowers. We identified microbes isolated from nectar of common tansy, Tanacetum vulgare , identified the microbial odorants, and tested their effect on attracting the common house mosquito, Culex pipiens . Results We collected 19 microbial isolates from T. vulgare nectar, representing at least 12 different taxa which we identified with 16S or 26S rDNA sequencing as well as by biochemical and physiological tests. Three microorganisms, Lachancea thermotolerans, Micrococcus lactis , Micrococcus luteus , were grown on culture medium and tested in bioassays. L. thermotolerans grown on nectar, malt extract agar, or in synthetic nectar broth significantly attracted C. pipiens females. The odorant profile produced by L. thermotolerans varied depending on the composition of the culture medium used. Surprisingly, all three microbes grown separately, but presented concurrently, attracted fewer C. pipiens females than L. thermotolerans by itself. Conclusions Floral nectar of T. vulgare contains various microbes whose odorants contribute to the odor profile of inflorescences. In addition, one of the microbes, the yeast L. thermotolerans, produced odorants that attract Cx. pipiens females. As the odor profile of L. thermotolerans varied with the composition of the culture medium, we hypothesize that microbe odorants inform nectar-foraging mosquitoes about the availability of certain macronutrients which, in turn, affect foraging decisions by mosquitoes.