Coexistence and competition effects on nectar microbe metabolite emission and pollinator acceptance

Authors: Rering, Caitlin; Beck, John; VANNETTE, RACHEL - University Of California, Davis; SCHAEFFER, ROBERT - University Of California, Davis

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 7/4/2018
Publication Date: 8/20/2018
Citation: Rering, C.C., Beck, J.J., Vannette, R.L., Schaeffer, R.N. 2018. Coexistence and competition effects on nectar microbe metabolite emission and pollinator acceptance. 256th American Chemical Society National Meeting. pg.1.

Interpretive Summary: Floral nectar often contains microorganisms like yeast and bacteria. The yeast Metschnikowia reukaufii is found in nectar across many plant species and throughout the world. Previously it was shown this yeast produces a unique blend of odors that does not repel honey bees, unlike the majority of studied microorganisms. However, nectar often contains more than one species and it is unknown whether this yeast will continue to produce the unique odor blend when grown with competitors. The effect of competition between Metschnikowia reukaufii and competing mircoorganisms in nectar was evaluated using chemical analysis and honey bee behavior tests. Results will be described.

Technical Abstract: Visitor-mediated pollination is necessary or beneficial for the majority of the world’s food crops, and nectar-inhabiting microorganisms, commonly reaching high cell densities (>106 cells µL-1), but low species richness (i.e. 1-2 strains per flower), contribute to floral scent and influence acceptance of flowers. Competition between nectar microbes has been evaluated to some extent, but volatile emission of microbial consortia and subsequent impacts on pollinator acceptance of nectars is not known. A frequently observed and widespread nectar-inhabiting yeast, Metschnikowia reukaufii, has been found to attract (or not repel) generalist pollinators, unlike many nectar microorganisms. The volatile blend produced by M. reukaufii, which includes a rich mix of fermentation volatiles (i.e., ethanol, 3-methyl-1-butanol) and notably, honey bee pheromones (i.e., isoamyl acetate, 1-hexanol) and floral volatiles (i.e., 2-phenylethanol, ethyl acetate), is thought to play an important role in mediating this pollinator response. To examine whether M. reukaufii produces its signature volatile blend under competitive pressure, the yeast was simultaneously introduced to synthetic nectar with a single bacteria competitor at identical cell densities. M. reukaufii was grown individually and in one:one combination with the nectar bacteria generalists Asaia astilbes and Neokomagataea. Metabolites (volatile and non-volatile) were screened over a 48 h duration. Survival and growth of the microorgansims was evaluated. Biofilm formation and bee acceptance of inoculated synthetic nectars was also compared among treatments. Not unexpectedly, all microorganisms survived and grew during the short incubation period. Volatile production in nectar differed significantly when M. reukaufii was grown in the presence of competitors.