Pollen extracts increase growth of a trypanosome parasite of bumble bees

Organismic and Evolutionary Biology, University of Massachusetts at Amherst, Amherst, MA, United States
Subject Areas
Ecology, Entomology, Parasitology, Plant Science, Infectious Diseases
Bombus, plant secondary metabolites, parasite, pollinator decline, Crithidia, nutrient limitation, antitrypanosomal, tritrophic interactions
© 2017 Palmer-Young
This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, reproduction and adaptation in any medium and for any purpose provided that it is properly attributed. For attribution, the original author(s), title, publication source (PeerJ Preprints) and either DOI or URL of the article must be cited.
Cite this article
Palmer-Young EC. 2017. Pollen extracts increase growth of a trypanosome parasite of bumble bees. PeerJ Preprints 5:e2730v1


Phytochemicals produced by plants, including at flowers, function in protection against plant diseases, and have a long history of use against trypanosome infection. Floral nectar and pollen, the sole food sources for many species of insect pollinators, contain phytochemicals that have been shown to reduce trypanosome infection in bumble and honey bees when fed as isolated compounds. Nectar and pollen, however, consist of phytochemical mixtures, which can have greater antimicrobial activity than do single compounds. This study tested the hypothesis that pollen extracts would inhibit parasite growth.Extracts of six different pollens were tested for direct inhibitory activity against cell cultures of the bumble bee trypanosome gut parasite Crithidia bombi.

Surprisingly, pollen extracts increased parasite growth rather than inhibiting it. Experimental manipulations of growth media showed that supplemental monosaccharides (glucose and fructose) were sufficient to promote growth, while a common floral phytochemical (caffeic acid) with inhibitory activity against other trypanosomes had only weak inhibitory effects on Crithidia bombi. These results indicate that, although pollen is essential for bees and other pollinators, pollen may promote growth of intestinal parasites that are uninhibited by pollen phytochemicals and, as a result, can benefit from the nutrients that pollen provides.

Author Comment

This is a submission to PeerJ for review.

Supplemental Information

Supplementary materials: Data files for effects of pollen on C. bombi

Dataset 1: Effects of extracts of individual pollens.

Dataset 2: Effects of individual and mixed pollen extracts.

Dataset 3: Effects of chemical additions.

"Row" and "column" refer to locations on the 96-well test plate

"conc" indicates the concentration in percent extract (or stock solution) by volume in the final sample

"net0" through "net24" are the net OD readings (difference in OD 630 nm between samples and cell-free controls at the corresponding concentration and timepoint) at each timepoint, with time given in hours.

"integral" is the estimated area under the curve of OD vs time, calculated by the "grofit" function in R

DOI: 10.7287/peerj.preprints.2730v1/supp-1

Supplementary Figures for Palmer-Young EC, Pollen extracts increase growth of a trypanosome parasite of bumble bees

Supplementary Figure 1. Growth curves for the individual pollen experiment.

Supplementary Figure 2. Growth curves for the mixed-pollen experiment

Supplemental figure 3. Growth curves for the chemical additions experiment.

DOI: 10.7287/peerj.preprints.2730v1/supp-2