Abstract
BackgroundSimilar to many other animals, the honey bee Apis mellifera relies on a beneficial gut microbiota for regulation of immune homeostasis. Honey bees exposed to agrochemicals, such as the herbicide glyphosate or antibiotics, usually exhibit dysbiosis and increased susceptibility to bacterial infection. Considering the relevance of the microbiota–immunity axis for host health, we hypothesized that glyphosate exposure could potentially affect other components of the honey bee physiology, such as the immune system.ResultsIn this study, we investigated whether glyphosate, besides affecting the gut microbiota, could compromise two components of honey bee innate immunity: the expression of genes encoding antimicrobial peptides (humoral immunity) and the melanization pathway (cellular immunity). We also compared the effects of glyphosate on the bee immune system with those of tylosin, an antibiotic commonly used in beekeeping. We found that both glyphosate and tylosin decreased the expression of some antimicrobial peptides, such as apidaecin, defensin and hymenoptaecin, in exposed honey bees, but only glyphosate was able to inhibit melanization in the bee hemolymph.ConclusionsExposure of honey bees to glyphosate or tylosin can reduce the abundance of beneficial gut bacteria and lead to immune dysregulation.
Highlights
Similar to many other animals, the honey bee Apis mellifera relies on a beneficial gut microbiota for regulation of immune homeostasis
Effects of glyphosate and tylosin on the transcriptome and microbiome of honey bees Considering that glyphosate or tylosin exposure affects the gut microbiota of honey bees [20,21,22,23,24], we decided to investigate whether these microbial perturbations could lead to other impacts on honey bee physiology
We initially investigated changes in the honey bee gut transcriptome due to glyphosate (0.1 or 1 mM) or tylosin (0.1 mM) exposure in experiments performed in fall 2018 and summer 2020 (Fig. 1)
Summary
Similar to many other animals, the honey bee Apis mellifera relies on a beneficial gut microbiota for regulation of immune homeostasis. Imbalances to the gut microbiota, commonly called dysbiosis, may lead to various negative consequences to hosts, culminating in poor development, immune dysregulation and disease [2]. These effects occur in many animals, including the Western honey bee, Apis mellifera, an important agricultural pollinator that relies on a beneficial gut microbiota to maintain homeostasis [3,4,5]. Experiments using gnotobiotic honey bees have demonstrated the importance of the native gut microbiota, including the contribution of specific bacterial members, such as Snodgrassella alvi and Frischella perrara, to the stimulation and regulation of the immune system [7,8,9]
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