Nectar-dwelling microbes of common tansy are attractive to its mosquito pollinator, Culex pipiens L.

Abstract

Background 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, elucidated the microbial odorants, and tested their ability to attract 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. Only the yeast L. thermotolerans grown on nectar, malt extract agar, or in synthetic nectar broth significantly attracted Cx. pipiens females. The odorant profile produced by L. thermotolerans varied with the nutritional composition of the culture medium. All three microbes grown separately, but presented concurrently, attracted fewer Cx. 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, 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 macro-nutrients which, in turn, affect foraging decisions by mosquitoes.

Colonization of Honey Bee Digestive Tracts by Environmental Yeast Lachancea thermotolerans Is Naturally Occurring, Temperature Dependent, and Impacts the Microbiome of Newly Emerged Bees

“…However, evidence has also been reported that honey bees even avoid yeast-laden nectar ( 45 ). Lachancea thermotolerans itself, when found on the common tansy, is attractive to the mosquito pollinator of this plant ( 46 ), providing one example where the yeast described here impacts pollinator preference. Thus, from an ecological standpoint, honey bee exposure to L. thermotolerans might be expected to be quite common in a manner dependent on local conditions.…”

Honeybees affect floral microbiome composition in a central food source for wild pollinators in boreal ecosystems

“…Floral microbiome is an understudied and underexplored ecological factor that affects pollinator attraction (Peach et al 2021 ; Russell and Ashman 2019 ) and thus pollination (Herrera et al 2013 ; Herrera and Medrano 2017 ) and plant reproduction (Yang et al 2019 ; Schaeffer and Irwin 2014 ; Vannette et al 2013 ), but also has consequences on the pollinators (Fürst et al 2014 ; Graystock et al 2015 ) with presently unknown ecological dimensions. Wild pollinator populations are globally declining at the same time as honeybee farming and trading is increasingly intensive.…”

Potential effects of nectar microbes on pollinator health

“…However, to our knowledge, little work has been done to address the influence of nectar microbes on non-bee flower visitors. Two studies on Dipteran species have revealed an attraction to nectar yeasts and bacteria: hoverflies and mosquitoes (Culex pipiens) are attracted to the bacterium Acinetobacter nectaris and nectar yeasts M. reukaufii and Lachancea thermotolerans, respectively [94,133]. Nectar sugars were not addressed in either of these studies though, with VOCs instead noted to play an important role in attraction.…”