Microbial Diversity Associated with the Pollen Stores of Captive-Bred Bumble Bee Colonies.

Prarthana S Dharampal,Chris Todd Hittinger,Juan Zalapa,Max A B Haase,Luis Diaz-Garcia,Shawn A Steffan,Cameron R Currie

doi:10.3390/insects11040250

Abstract

The pollen stores of bumble bees host diverse microbiota that influence overall colony fitness. Yet, the taxonomic identity of these symbiotic microbes is relatively unknown. In this descriptive study, we characterized the microbial community of pollen provisions within captive-bred bumble bee hives obtained from two commercial suppliers located in North America. Findings from 16S rRNA and ITS gene-based analyses revealed that pollen provisions from the captive-bred hives shared several microbial taxa that have been previously detected among wild populations. While diverse microbes across phyla Firmicutes, Proteobacteria, Bacteroidetes, Actinobacteria, and Ascomycota were detected in all commercial hives, significant differences were detected at finer-scale taxonomic resolution based on the supplier source. The causative agent of chalkbrood disease in honey bees, Ascosphaera apis, was detected in all hives obtained from one supplier source, although none of the hives showed symptoms of infection. The shared core microbiota across both commercial supplier sources consisted of two ubiquitous bee-associated groups, Lactobacillus and Wickerhamiella/Starmerella clade yeasts that potentially contribute to the beneficial function of the microbiome of bumble bee pollen provisions.

Highlights

Organisms across the tree of life span a continuum of reliance on microbial symbionts [1,2], collectively referred to as their “microbiome” [3,4]
The specific aims of this study were to: (1) characterize and compare the taxonomic diversity of bacteria and fungi within the pollen provisions of bumble bee hives obtained from the two supplier sources, (2) identify the “core microbiome” within the pollen provisions, and (3) use publicly available data to compare the bacterial community of bumble bee pollen provisions with that of the bumble bee gut and other insect–microbe symbioses
Bacteria detected from pollen provisions included members of four phyla (Firmicutes, Proteobacteria, Bacteroidetes, Actinobacteria)

Summary

Introduction

Organisms across the tree of life span a continuum of reliance on microbial symbionts [1,2], collectively referred to as their “microbiome” [3,4]. Host–microbiome interactions can range from mutualistic to pathogenic [2] depending on the taxonomic and functional composition of the microbiome. Non-pathogenic symbionts allow hosts to obtain nutrients from inaccessible substrates [5], utilize novel energy sources [6], and thrive in extreme habitats [7]. Hosts that derive nutritional benefits from their symbionts often demonstrate increased dependence on their microbial partners [8]. Extreme dependence on nutritional mutualists has led to major evolutionary transitions among several eukaryotic hosts [9]. The overall fitness of Insects 2020, 11, 250; doi:10.3390/insects11040250 www.mdpi.com/journal/insects

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