Abstract
Honey bees (Apis mellifera) are the primary pollinators of major horticultural crops. Over the last few decades, a substantial decline in honey bees and their colonies have been reported. While a plethora of factors could contribute to the putative decline, pathogens, and pesticides are common concerns that draw attention. In addition to potential direct effects on honey bees, indirect pesticide effects could include alteration of essential gut microbial communities and symbionts that are important to honey bee health (e.g., immune system). The primary objective of this study was to determine the microbiome associated with honey bees exposed to commonly used in-hive pesticides: coumaphos, tau-fluvalinate, and chlorothalonil. Treatments were replicated at three independent locations near Blacksburg Virginia, and included a no-pesticide amended control at each location. The microbiome was characterized through pyrosequencing of V2–V3 regions of the bacterial 16S rRNA gene and fungal ITS region. Pesticide exposure significantly affected the structure of bacterial but not fungal communities. The bee bacteriome, similar to other studies, was dominated by sequences derived from Bacilli, Actinobacteria, α-, β-, γ-proteobacteria. The fungal community sequences were dominated by Ascomycetes and Basidiomycetes. The Multi-response permutation procedures (MRPP) and subsequent Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) analysis indicated that chlorothalonil caused significant change to the structure and functional potential of the honey bee gut bacterial community relative to control. Putative genes for oxidative phosphorylation, for example, increased while sugar metabolism and peptidase potential declined in the microbiome of chlorothalonil exposed bees. The results of this field-based study suggest the potential for pesticide induced changes to the honey bee gut microbiome that warrant further investigation.
Highlights
As pollinators and honey producers, honey bees (Apis mellifera) are vital to global agriculture
The results highlight the potential that changing microbial community structure may have on the functional ability of the microbiome to metabolize sugars and peptides, presumably vital processes contributing to honey bee health
Results of the current study suggest that pesticides such as chlorothalonil have the potential to alter the gut microbiota and its function
Summary
As pollinators and honey producers, honey bees (Apis mellifera) are vital to global agriculture. There is a need to determine the potential influence of these commonly used chemicals on honey bees and associated gut symbionts. Honey bees and associated gut microbiota are exposed to pesticides applied to agricultural lands. A latest survey has identified multiple pesticide residues, both beekeeper and grower applied, in honey bee hives (Mullin et al, 2010). While in-hive application is needed to help control parasites and pathogens, the potential lethal effects of these chemicals could have unwanted side effects (Johnson et al, 2010). Questions have been raised about the potential for changes to the gut microflora of honey bees following pesticide exposure, field scale observations of pesticide effects at multiple locations have not been conducted
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