Microbiota dysbiosis in honeybee ( Apis mellifera L . ) larvae infected with brood diseases and foraging bees exposed to agrochemicals

Abstract

American foulbrood (AFB) disease and chalkbrood disease (CBD) are important bacterial and fungal diseases, respectively, that affect honeybee broods. Exposure to agrochemicals is an abiotic stressor that potentially weakens honeybee colonies. Gut microflora alterations in adult honeybees associated with these biotic and abiotic factors have been investigated. However, microbial compositions in AFB- and CBD-infected larvae and the profile of whole-body microbiota in foraging bees exposed to agrochemicals have not been fully studied. In this study, bacterial and fungal communities in healthy and diseased (AFB/CBD) honeybee larvae were characterized by amplicon sequencing of bacterial 16S rRNA gene and fungal internal transcribed spacer1 region, respectively. The bacterial and fungal communities in disordered foraging bees poisoned by agrochemicals were analysed. Our results revealed that healthy larvae were significantly enriched in bacterial genera Lactobacillus and Stenotrophomonas and the fungal genera Alternaria and Aspergillus . The enrichment of these microorganisms, which had antagonistic activities against the etiologic agents for AFB and CBD, respectively, may protect larvae from potential infection. In disordered foraging bees, the relative abundance of bacterial genus Gilliamella and fungal species Cystofilobasidium macerans were significantly reduced, which may compromise hosts' capacities in nutrient absorption and immune defence against pathogens. Significantly higher frequency of environmentally derived fungi was observed in disordered foraging bees, which reflected the perturbed microbiota communities of hosts. Results from PICRUSt and FUNGuild analyses revealed significant differences in gene clusters of bacterial communities and fungal function profiles. Overall, results of this study provide references for the composition and function of microbial communities in AFB- and CBD-infected honeybee larvae and foraging bees exposed to agrochemicals.

A Snapshot Picture of the Fungal Composition of Bee Bread in Four Locations in Bulgaria, Differing in Anthropogenic Influence

“…They are important species, playing roles within the beehives, similar to those of Cladosporium and Penicillium species. Their widespread occurrence could also be supported by the recent findings that they possess the potential to inhibit the growth of the causative agents of the American foulbrood disease (AFB) and chalkbrood disease (CBD) [18].…”

“…More strikingly, when the samples were taken, the beekeeper selected hives that in his opinion were healthy. One possible explanation of the observed paradox is the ability of Alternaria and some lactic acid bacteria to inhibit the growth of this pathogen [18,54]. Members of the Golovinomyces are strict plant pathogens [55], and, until now, they have never been reported to be associated with bees and bee products.…”

“…Many of these have an ambiguous nature acting as probiotics [13] and/or shaping the bees' health and fitness [14] but also being producers of mycotoxins [15,16]. However, available data suggest that their positive influence overcomes the negative one, at least for the beehives [13,17,18].…”

“…available data suggest that their positive influence overcomes the negative one, at least for the beehives [13,17,18].…”

Functional Properties and Antimicrobial Activity from Lactic Acid Bacteria as Resources to Improve the Health and Welfare of Honey Bees

“…Pesticides, such as insecticides and fungicides, are considered one of the possible stressors causing the general decline in honey bees and colony losses [ 5 , 12 , 119 ]. The exposure of honey bees to pesticides also causes microbial dysbiosis and immunosuppression, rendering them more susceptible to pathogens; furthermore, the interactions between pesticides and pathogens may exacerbate honey bees’ mortality [ 120 , 121 , 122 , 123 , 124 , 125 , 126 , 127 , 128 , 129 , 130 ]. A novel concept may be the administration of lactic acid bacteria to mitigate the harmful effects of pesticides.…”