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Animals such as bumblebees use chemosensory cues to both locate and evaluate essential resources. Increasingly, it is recognized that microbes can alter the quality of foraged resources and produce metabolites that may act as foraging cues. The distinct nature of these chemosensory cues however and their use in animal foraging remain poorly understood. Here, we test the hypothesis that species of nectar-inhabiting microbes differentially influence pollinator attraction and feeding via microbial metabolites produced in nectar. We first examined the electrophysiological potential for bumblebee (Bombus impatiens) antennal olfactory neurons to respond to microbial volatile organic compounds (mVOCs), followed by an olfactory preference test. We also assessed gustatory preferences for microbial-altered nectar through both no-choice and choice feeding assays. Antennal olfactory neurons responded to some mVOCs, and bees preferred nectar solutions inoculated with the bacterium Asaia astilbes over the yeast Metschnikowia reukaufii based on volatiles alone. However, B. impatiens foragers consumed significantly more Metschnikowia-inoculated nectar, suggesting distinct roles for mVOCs and non-volatile metabolites in mediating both attraction and feeding decisions. Collectively, our results suggest that microbial metabolites have significant potential to shape interspecific, plant-pollinator signalling, with consequences for forager learning, economics and floral host reproduction.

The plant microbiome can influence plant phenotype in diverse ways, yet microbial contribution to plant volatile phenotype remains poorly understood. We examine the presence of fungi and bacteria in the nectar of a coflowering plant community, characterize the volatiles produced by common nectar microbes and examine their influence on pollinator preference. Nectar was sampled for the presence of nectar-inhabiting microbes. We characterized the headspace of four common fungi and bacteria in a nectar analog. We examined electrophysiological and behavioral responses of honey bees to microbial volatiles. Floral headspace samples collected in the field were surveyed for the presence of microbial volatiles. Microbes commonly inhabit floral nectar and the common species differ in volatile profiles. Honey bees detected most microbial volatiles tested and distinguished among solutions based on volatiles only. Floral headspace samples contained microbial-associated volatiles, with 2-ethyl-1-hexanol and 2-nonanone - both detected by bees - more often detected when fungi were abundant. Nectar-inhabiting microorganisms produce volatile compounds, which can differentially affect honey bee preference. The yeast Metschnikowia reukaufii produced distinctive compounds and was the most attractive of all microbes compared. The variable presence of microbes may provide volatile cues that influence plant-pollinator interactions.

Nectar microbe-produced volatiles can contribute to floral blends and modify pollinator preference for flowers. Identifying and describing the compounds that may underlie this effect is a key goal. Semi-quantitative or quantitative data is often critical for chemical ecology investigations, given that biotic responses (i.e., insects or plants) can fluctuate with concentration, relative ratios, or composition of the emitted volatile profiles. However, field-based, in situ microbial volatile detection and quantification is difficult due to the small scale of the nectar microhabitat. Laboratory-based inoculations of bulk synthetic nectars are useful for screening weakly-abundant and difficult to analyze volatiles, which may be crucial in eliciting responses. Despite the limitations of this approach, it allows rapid identification of target molecules for further validation with bioassays. Targeted analytical methods to identify or quantify semiochemicals may then be developed and validated for field tests. Here, we report the first quantitative assessment of microbe volatile emission in laboratory-based tests with synthetic nectar. We also review briefly solid-phase microextraction collection and gas-chromatography data interpretation. Nectar microbe interactions with plants and insects offer opportunities for agricultural improvement, and a selection of potential uses are highlighted.

Insect pests cause serious economic, yield, and food safety problems to managed crops worldwide. Compounding these problems, insect pests often vector pathogenic or toxigenic microbes to plants. Previous work has considered plant-insect and plant-microbe interactions separately. Although insects are well-understood to use plant volatiles to locate hosts, microorganisms can produce distinct and abundant volatile compounds that in some cases strongly attract insects. In this paper, we focus on the microbial contribution to plant volatile blends, highlighting the compounds emitted and the potential for variation in microbial emission. We suggest that these aspects of microbial volatile emission may make these compounds ideal for use in agricultural applications, as they may be more specific or enhance methods currently used in insect control or monitoring. Our survey of microbial volatiles in insect-plant interactions suggests that these emissions not only signal host suitability but may indicate a distinctive time frame for optimal conditions for both insect and microbe. Exploitation of these host-specific microbe semiochemicals may provide important microbe- and host-based attractants and a basis for future plant-insect-microbe chemical ecology investigations.

'An EHR ... doesn't necessarily make you a better practice or make you more profitable' ('Staffing: How will new technologies affect your need for personnel?' [by Liz Meszaros], June 4 [...]