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Missing Microbes in Bees: How Systematic Depletion of Key Symbionts Erodes Immunity
Abstract and Figures
Pesticide exposure, infectious disease, and nutritional stress contribute to honey bee mortality and a high rate of colony loss. This realization has fueled a decades-long investigation into the single and combined effects of each stressor and their overall bearing on insect physiology. However, one element largely missing from this research effort has been the evaluation of underlying microbial communities in resisting environmental stressors and their influence on host immunity and disease tolerance. In humans, multigenerational bombardment by antibiotics is linked with many contemporary diseases. Here, we draw a parallel conclusion for the case in honey bees and suggest that chronic exposure to antimicrobial xenobiotics can systematically deplete honey bees of their microbes and hamper cross-generational preservation of host-adapted symbionts that are crucial to health.
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... It is noteworthy to mention that, at high concentrations, some antibiotics can exert toxic effects on honey bee physiology [28]. Although, a more pertinent concern in most cases is the off-target effects on microbial symbionts and the subsequent impacts this can have on bee metabolism and immunity [29]. Given the well-known digestive roles of the gut microbiota [30], it is conceivable that antibiotic exposure could also interfere with honey bee nutritional status. ...
... In terms of pure isolates, bacterial symbionts from both adults and larvae (including Apilactobacillus kunkeei) have demonstrated inhibitory effects on P. larvae in vitro [47,48], indicating that the larval microbiota also has potential to protect against infection. It is possible then, that the depletion or delayed acquisition of these bacteriafor example, due to antibiotic exposure, pesticides, or environmental factors [29] may allow for P. larvae germination and subsequent AFB disease transition. During a natural AFB outbreak in Ontario, Daisley et al. [49] found that third-to-fifth instar larvae from colonies presenting clinical signs and symptoms had almost undetectable levels of A. kunkeei (~10 2 or fewer target gene copies based on qPCR quantification with species-specific primers). ...
... Interestingly, despite being highly hostadapted, P. larvae is susceptible to both honey bee AMPs (e.g., Defensin-1) and metabolites from bacterial symbionts [61], perhaps explaining why it has evolved to specifically attack first-tosecond instar larvae that have underdeveloped immune systems and inconsistent microbiota profiles [5]. It is noteworthy to mention that bacterial symbionts (especially Lactobacillus and Snodgrassella spp.) play a crucial role in honey bee immune regulation, and thus maintenance of healthy immune signaling and microbiota functioning is in reality a bidirectional process biologically favoring healthy homeostasis and disease resistance [29]. Cumulatively, this indicates that an optimal way to improve resistance to AFB (and potentially other bacterial diseases) is to support the natural immune and microbiota defense systems of honey bees. ...
Paenibacillus larvae is a spore-forming bacterial entomopathogen and causal agent of the important honey bee larval disease, American foulbrood (AFB). Active infections by vegetative P. larvae are often deadly, highly transmissible, and incurable for colonies but, when dormant, the spore form of this pathogen can persist asymptomatically for years. Despite intensive investigation over the past century, this process has remained enigmatic. Here, we provide an up-to-date synthesis on the often overlooked microbiota factors involved in the spore-to-vegetative growth transition (corresponding with the onset of AFB disease symptoms) and offer a novel outlook on AFB pathogenesis by focusing on the 'collaborative' and 'competitive' interactions between P. larvae and other honey bee-adapted microorganisms. Furthermore, we discuss the health trade-offs associated with chronic antibiotic exposure and propose new avenues for the sustainable control of AFB via probiotic and microbiota management strategies.
... Many stress factors have been proposed and can be physical, chemical, nutritional, microbiological, and psychosocial. Stress may be generated by the perception of danger, a pathogen or parasite attack, nutrient deficiency, malnutrition, metabolic imbalance, microbiota disruption, or dysfunctional metabolic homeostasis induced by physical challenges: climate change, heat, cold, drought, and toxins (e.g., pesticides, antibiotics, heavy metals, air pollution, nanoparticles, plastics) ( Figure 2) [9,11,13,14,[16][17][18][19][20][21][22]24,[27][28][29][30]39,[42][43][44][45][46][47][48][49][50][51][52][53][54][55][56]. Based on the current evidence showing that honeybees and colonies are under the influence of numerous factors, a key question is: Could unravelling all those complex interactions allow the scientific community to set strategies that would help beekeepers reduce the loss of colonies ? ...
... Among these, we can cite exposure to pesticides from agriculture or even beekeeping activities, the loss of floral biodiversity on farmlands, seasonal changes, climate changes, and any environmental stress. In addition, external stressors and some internal stressors have been described that can affect the general survival of a colony [13,16,24,37,57]. The most common factors are parasites (Varroa destructor), microbial pathogens (Paenibacillus larvae, Melissococcus plutonius), malnutrition, and genetics ( Figure 2). ...
... Over the last two decades, the microbiota has been largely studied in the context of human health and is linked with numerous pathological situations [8,11,17,[22][23][24]28,32,33,35,43,48,50,. Interestingly, the microbiota is also seen as a cornerstone to honeybee health, as for so many other living organisms. ...
Climate change, loss of plant biodiversity, burdens caused by new pathogens, predators, and toxins due to human disturbance and activity are significant causes of the loss of bee colonies and wild bees. The aim of this review is to highlight some possible strategies that could help develop bee resilience in facing their changing environments. Scientists underline the importance of the links between nutrition, microbiota, and immune and neuroendocrine stress resistance of bees. Nutrition with special care for plant-derived molecules may play a major role in bee colony health. Studies have highlighted the importance of pollen, essential oils, plant resins, and leaves or fungi as sources of fundamental nutrients for the development and longevity of a honeybee colony. The microbiota is also considered as a key factor in bee physiology and a cornerstone between nutrition, metabolism, growth, health, and pathogen resistance. Another stressor is the varroa mite parasite. This parasite is a major concern for beekeepers and needs specific strategies to reduce its severe impact on honeybees. Here we discuss how helping bees to thrive, especially through changing environments, is of great concern for beekeepers and scientists.
... Nowadays, studies on the gut microbiota of pollinators have clarified the role of the genera Bifidobacterium and Lactobacillus in immunity preservation, disease tolerance and resistance to environmental stressors [15]. The core of honey bees' gut microbiota, whatever their geographical origin, is composed of Gilliamella apicola, Lactobacillus Firm-5 (L. ...
... mellis, L. mellifer), Snodgrassella alvi and Bifidobacterium asteroides [16]. The gut microbiota and its symbiotic bacteria exert a key role in the innate immunity system of bees, despite the production of antimicrobial peptides with a highly selective activity against pathogenic species [15]. The disruption of the microbial balance in the bee's gut is due to the perturbation of insect immunity through treatments with microbicidal or microbiostatic compounds; the exposure to pesticides or herbicides at a sublethal concentration (called hidden treatment) leads to a decrease in Firmicutes and Actinobacteria and to an increase in Gammaproteobacteria, such as Gilliamella apicola and Escherichia coli. ...
... Differently from other insects, such as ants, whose microbiota is acquired from food and the environment, honeybees, similarly to humans, have a gut microbiota with a stable core that, after the early developmental stages, remains relatively stable through most of their adult lifetime [50]. It has recently been discovered that the phyla that constitute the core of honeybee gut microbiota are three of the most important components of human gut microbiota (Firmicutes, Proteobacteria, Actinobacteria) [15]. Several studies using 16S rDNA surveys and metagenomic of the total DNA, highlighted that Bifidobacterium asteroides, along with Lactobacillus FIRM4 and Lactobacillus FIRM5, represent the so-called core-bacteria, as the most essential microorganism in the honeybee gut and these evidence could be related to a possible probiotic potential of Bifidobacterium asteroides strains [49][50][51][52]. ...
Bifidobacteria have long been recognized as bacteria with probiotic and therapeutic features. The aim of this work is to characterize the Bifidobacterium asteroides BA15 and BA17 strains, isolated from honeybee gut, to evaluate its safety for human use. An in-depth assessment was carried out on safety properties (antibiotic resistance profiling, β-hemolytic, DNase and gelatinase activities and virulence factor presence) and other properties (antimicrobial activity, auto-aggregation, co-aggregation and hydrophobicity). Based on phenotypic and genotypic characterization, both strains satisfied all the safety requirements. More specifically, genome analysis showed the absence of genes encoding for glycopeptide (vanA, vanB, vanC-1, vanC-2, vanD, vanE, vanG), resistance to tetracycline (tetM, tetL and tetO) and virulence genes (asa1, gelE, cylA, esp, hyl).
... The annual cycle of a bee colony consists of two periods: The first is the honey flow period, when honey bees are mainly outside the hive and contact the environmental microflora. The second is the overwintering period when honey bees are inside the hive and contact the hive microflora and colony members (Daisley et al., 2020). During the overwintering period, the bee colony cannot defecate, which results in various infections (Kwong and Moran, 2016). ...
... Ascosphaerosis is an infectious disease of bee colonies caused by the parasitic fungus Ascosphaera apis, affecting bee larvae (Crotti et al., 2013;Tejerina et al., 2020). The fungal spores get into apiary bee colonies mainly with pollen and nectar (Daisley et al., 2020;Tejerina et al., 2020). Ascospherosis in the bee colony results in the dead larvae, producing no population succession among adult bees, dramatically reducing the total number of honey bees and the bee colony losses (Kwong and Moran, 2016). ...
... Crotti et al. (2013) and Kwong and Moran (2016) stated the significance of the relative constancy in the honey bee gut microbiocenosis. The present study has revealed the instability of the microbiocenosis during overwintering, which can weaken the collective immunity in a bee colony (Daisley et al., 2020). Probiotics and plant extract preparations (Ilyasov and Farkhutdinov, 2016;Yumaguzhin et al., 2020) can be effective in this case. ...
... It has also been reported that oxalic acid, used by the beekeepers in Varroa control treatment, can produce a number of problems to beehives, including a reduced longevity (Rademacher et al., 2017). On the other hand, the constant use of antibiotics can alter the microbiota present in bees, which may have a negative impact in their immune system (Daisley et al., 2020). The immune system of bees includes a physical and a humoral barrier (Tihelka, 2018). ...
... Considering the above, the constant use of the presently used treatments, although being effective against pathogens, involve several adverse effects including flight, the reproductive capacity of queens, ability to learn, reduced pollinizing capacity and affected communication capacities (Daisley et al., 2020;Larsen et al., 2019;Mullin et al., 2010). Therefore, it is important to search for new alternatives capable to be a complement or a substitute to the present-day options. ...
Considering the economic and environmental role played by bees and their present threats it is necessary to develop food supplements favoring their health. The aim of this work was to isolate and characterize an immunomodulating probiotic capable to improve the health of honeybee colonies. For this purpose, bacterial strains were isolated from Apis mellifera bees (N = 180) obtained at three apiaries. A total of 44 strains were isolated and 9 of them were identified as Lactobacillus having the capacity to grow under saccharose osmotic stress, at pH 4.0 and possessing a wide susceptibility to antibiotics. Results allowed to select two strains but finally only one of them, strain A14.2 showed a very significant immunomodulating activity. This strain increased the expression of mRNA codifying the antimicrobial peptides 24 h post-administration. We evaluated its growth kinetics under aerobic and microaerobic conditions and its survival in the presence of high concentrations of saccharose. Results demonstrated that Lactobacillus casei A14.2 strain was highly tolerant to oxygen and that it was able to adapt to saccharose enriched environments (50% and 100% w/v). Finally, L. casei A14.2 strain was administered monthly during summer and early fall to 4 honeybee colonies (2 controls and 2 treatments). The results showed a gradual sustained decrease of infestation (p < 0.05) by the pathogenic Nosema spp. but no reduction in the infestation by the mite Varroa destructor. These results suggest that the administration of this potential probiotic, may increase the resistance of honeybee colonies to infectious diseases caused by Nosema spp.
... Gut bacteria also stimulate the honeybee innate immune system, which might be a host mechanism to regulate the microbiota [10]. Symbiont-mediated stimulation of the innate immune system in honeybees results in the production of host antimicrobial peptides that can differentially modulate microbial constituents in favor of particular core members and protect against pathogens [11]. ...
... Nutritional stressors affect the health of bees by intersecting at the gut microbiome [11,49]. Although we did not find significant differences in the composition bacterial associated microbiota of foragers from diseased colonies, PERMANOVA interactions suggest that the gut microbiota temporal changes differ between healthy and diseased colonies. ...
Compared to honeybees and bumblebees, the effect of diet on the gut microbiome of Neotropical corbiculate bees such as Melipona spp. is largely unknown. These bees have been managed for centuries, but recently an annual disease is affecting M. quadrifasciata, an endangered species kept exclusively by management in Southern Brazil. Here we report the results of a longitudinal metabarcoding study involving the period of M. quadrifasciata colony weakness, designed to monitor the gut microbiota and diet changes preceding an outbreak. We found increasing amounts of bacteria associated to the gut of forager bees 2 months before the first symptoms have been recorded. Simultaneously, forager bees showed decreasing body weight. The accelerated growth of gut-associated bacteria was uneven among taxa, with Bifidobacteriaceae dominating, and Lactobacillaceae decreasing in relative abundance within the bacterial community. Dominant fungi such as Candida and Starmerella also decreased in numbers, and the stingless bee obligate symbiont Zygosaccharomyces showed the lowest relative abundance during the outbreak period. Such changes were associated with pronounced diet shifts, i.e., the rise of Eucalyptus spp. pollen amount in forager bees’ guts. Furthermore, there was a negative correlation between the amount of Eucalyptus pollen in diets and the abundance of some bacterial taxa in the gut-associated microbiota. We conclude that diet and subsequent interactions with the gut microbiome are key environmental components of the annual disease and propose the use of diet supplementation as means to sustain the activity of stingless bee keeping as well as native bee pollination services.
... A wide range of xenobiotics can affect size, composition and functional properties of the honey bee gut microbiota (Daisley et al., 2020), as it has been demonstrated for pesticides (i.e., glyphosate, Motta et al., 2018), airborne particular matters (i.e., titanium dioxide, Papa et al., 2021) and antibiotics (e.g., tetracycline, Raymann et al., 2017). In certain countries, including the United States, antibiotics, mainly tetracycline derivates, are applied in apiculture as a preventive or control measure against two common larval diseases, American and European Foulbrood, caused by Paenibacillus larvae and Melissococcus plutonius, respectively (Genersch, 2010;Tian et al., 2012;Daisley et al., 2020). ...
... A wide range of xenobiotics can affect size, composition and functional properties of the honey bee gut microbiota (Daisley et al., 2020), as it has been demonstrated for pesticides (i.e., glyphosate, Motta et al., 2018), airborne particular matters (i.e., titanium dioxide, Papa et al., 2021) and antibiotics (e.g., tetracycline, Raymann et al., 2017). In certain countries, including the United States, antibiotics, mainly tetracycline derivates, are applied in apiculture as a preventive or control measure against two common larval diseases, American and European Foulbrood, caused by Paenibacillus larvae and Melissococcus plutonius, respectively (Genersch, 2010;Tian et al., 2012;Daisley et al., 2020). The accumulation and permanent exposure of honey bees to such broad-spectrum antibiotics affect the composition, diversity and functionality of the exposed honey bee's gut microbiota (e.g., Raymann et al., 2017). ...
Gut microbiota are known to foster pollen digestion in honey bee workers, Apis mellifera, thereby enhancing longevity and body weight gain. However, it is currently not known how longevity and body weight gain are effected when gut microbiota are reduced in bees with or without access to pollen. Here, using a hoarding cage setup with freshly emerged summer workers, we manipulated the gut microbiota of half the bees with the antibiotic tetracycline (ABX), and left the other half untreated on a sucrose solution diet. Afterwards, all bees were assigned to either sucrose diets or sucrose plus ad libitum access to pollen (N = 4 treatments, N = 26 bees/treatment, N = 10 replicates/treatment, N = 1,040 total workers). The data confirm that pollen has a positive effect on longevity and body weight in workers with an unmanipulated gut microbiota. Surprisingly, the antibiotics alone also improved the longevity and body weight of the workers fed a strictly sucrose diet, potentially explained by the reduction of harmful bacteria. However, this positive effect was reversed from an observed antagonistic interaction between pollen and antibiotics, underscoring the innate value of natural microbiota on pollen digestion. In conclusion, a combination of adequate pollen supply and an unmanipulated gut microbiota appears crucial to honey bee worker health, calling for respective efforts to ensure both in managed colonies.
... glyphosate, thiamethoxam [neonicotinoid], imidacloprid [neonicotinoid], fipronil [phenylpyrazole], boscalid [carboxamide]; chlorpyrifos-methyl [phosphorganic]) poses a serious threat to the structure and composition of honeybee intestinal community, in a dose-dependent manner (Favaro et al., 2019;Rouz e et al., 2019;Motta and Moran, 2020;Paris et al., 2020). The capacity of agrochemicals to affect the microbial communities naturally co-evolving with honeybees may be much higher than currently appreciated (Daisley et al., 2020a;Cuesta-Mat e et al., 2021). As a consequence, promising strategies aiming to support honeybees' health status were proposed based on the management of the natural eubiotic bee microbiome (Baffoni et al., 2016;Daisley et al., 2020a). ...
... The capacity of agrochemicals to affect the microbial communities naturally co-evolving with honeybees may be much higher than currently appreciated (Daisley et al., 2020a;Cuesta-Mat e et al., 2021). As a consequence, promising strategies aiming to support honeybees' health status were proposed based on the management of the natural eubiotic bee microbiome (Baffoni et al., 2016;Daisley et al., 2020a). Fructophilic lactobacilli like Fructobacillus fructosus, Apilactobacillus apinorum and, especially, Apilactobacillus kunkeei are inhabitants of honeybee crop, which is located between oesophagus and proventriculus (Anderson et al., 2011(Anderson et al., , 2013Corby-Harris et al., 2014;Filannino et al., 2016). ...
The alteration of a eubiosis status in honeybees' gut microbiota is directly linked to the occurrence of diseases, and likely to the honeybees decline. Since fructophilic lactobacilli were suggested as symbionts for honeybees, we mechanistically investigated their behaviour under the exposure to agrochemicals (Roundup, Mediator and Reldan containing glyphosate, imidacloprid and chlorpyrifos-methyl as active ingredients respectively) and plant secondary metabolites (nicotine and p-coumaric acid) ingested by honeybees as part of their diet. The effects of exposure to agrochemicals and plant secondary metabolites were assessed both on planktonic cells and sessile communities of three biofilm-forming strains of Apilactobacillus kunkeei. We identified the high sensitivity of A. kunkeei planktonic cells to Roundup and Reldan, while cells embedded in mature biofilms had increased resistance to the same agrochemicals. However, agrochemicals still exerted a substantial inhibitory/control effect if the exposure was during the preliminary steps of biofilm formation. The level of susceptibility resulted to be strain-specific. Exopolysaccharides resulted in the main component of extracellular polymeric matrix (ECM) in biofilm, but the exposure to Roundup caused a change in ECM production and composition. Nicotine and p-coumaric acid had a growth-promoting effect in sessile communities, although no effect was found on planktonic growth.
... Gut bacteria also stimulate the honeybee innate immune system, which might be a host mechanism to regulate the microbiota [10]. Symbiont-mediated stimulation of the innate immune system in honeybees results in the production of host antimicrobial peptides that can differentially modulate microbial constituents in favor of particular core members and protect against pathogens [11]. ...
... Nutritional stressors affect the health of bees by intersecting at the gut microbiome [11,49]. Although we did not find significant differences in the composition bacterial associated microbiota of foragers from diseased colonies, PERMANOVA interactions suggest that the gut microbiota temporal changes differ between healthy and diseased colonies. ...
Compared to honeybees and bumblebees, the effect of diet on the gut microbiome of Neotropical corbiculate bees such as Melipona spp. is largely unknown. These bees have been managed for centuries, but recently an annual disease is affecting M. quadrifasciata , an endangered species kept exclusively by management in Southern Brazil. Here we report the results of a longitudinal metabarcoding study involving the period of M. quadrifasciata colony weakness, designed to monitor the gut microbiota and diet changes preceding an outbreak. We found increasing amounts of bacteria associated to the gut of forager bees two months before the first symptoms have been recorded. Simultaneously, forager bees showed decreasing body weight. The accelerated growth of gut-associated bacteria was uneven among taxa, with Bifidobacteriaceae dominating, and Lactobacillaceae decreasing in relative abundance within the bacterial community. Dominant fungi such as Candida and Starmerella also decreased in numbers, and the stingless bee obligate symbiont Zygosaccharomyces showed the lowest relative abundance during the outbreak period. Such changes were associated with pronounced diet shifts, i.e. , the rise of Eucalyptus spp. pollen amount in forager bees’ guts. Furthermore, there was a negative correlation between the amount of Eucalyptus pollen in diets and the abundance of some bacterial taxa in the gut associated microbiota. We conclude that diet and subsequent interactions with the gut microbiome are key environmental components of the annual disease, and propose the use of diet supplementation as means to sustain the activity of stingless bee keeping as well as native bee pollination services.
... Bee larvae immunity may be mediated through microbial communities in their guts, therefore, pesticides that influence these communities could influence brood disease susceptibility. Microbial communities in the guts of adult honey bees can play important roles in development, nutrient acquisition, and pathogen avoidance (Daisley et al., 2020a). Shifts in the microbial communities in adults can lead to dysbiosis, which is characterised by a loss of functionally important microbes in bee guts (Anderson and Ricigliano, 2017). ...
... To understand the effects pesticides and pathogens have on brood health, further work should examine the role of microbial symbionts in mediating their interactions. If microbes affect the interaction between pesticide and brood pathogens, this could pave the way for the use of probiotic supplements to alleviate the effects of these stressors in managed bee species (Daisley et al., 2020a;Daisley et al., 2020b;Floyd et al., 2020). Furthermore, given the importance of adult bees to brood health, researchers could utilise the more easily accessible adult bees as bioindicators of brood infections. ...
Brood diseases and pesticides can reduce the survival of bee larvae, reduce bee populations, and negatively influence ecosystem biodiversity. However, major gaps persist in our knowledge regarding the routes and implications of co-exposure to these stressors in managed and wild bee brood. In this review, we evaluate the likelihood for co-exposure to brood pathogen and pesticide stressors by examining the routes of potential co-exposure and the possibility for pollen and nectar contaminated with pathogens and pesticides to become integrated into brood food. Furthermore, we highlight ways in which pesticides may increase brood disease morbidity directly, through manipulating host immunity, and indirectly through disrupting microbial communities in the guts of larvae, or compromising brood care provided by adult bees. Lastly, we quantify the prevalence of a brood research bias to Apis species and discuss the implications the bias has on brood disease and pesticide risk assessment in wild bee communities. We advise that future studies should place a higher emphasis on evaluating bee brood afflictions and their interactions with commonly encountered stressors, especially in wild bee species.
... Intestinal dysbiosis, compositional and functional alteration of the microbiome, is associated with various diseases and health problems in humans and vertebrates (De Gruttola et al. 2016, Levy et al. 2017, Shreiner et al. 2015. In insects, dysbiosis negatively affects reproductive fitness, immunity, and resistance to pathogens (Ami et al. 2010, Daisley et al. 2020, Raymann et al. 2017). ...
Insect decline is a major threat for ecosystems around the world as they provide many important functions, such as pollination or pest control. Pollution is one of the main reasons for the decline, besides changes in land use, global warming, and invasive species. While negative impacts of pesticides are well studied, there is still a lack of knowledge about the effects of other anthropogenic pollutants, such as airborne particulate matter, on insects. To address this, we exposed workers of the bumblebee Bombus terrestris to sublethal doses of diesel exhaust particles (DEPs) and brake dust, orally or via air. After seven days, we looked at the composition of the gut microbiome and tracked changes in gene expression. While there were no changes in the other treatments, oral DEP exposure significantly altered the structure of the gut microbiome. In particular, the core bacterium Snodgrassella had a decreased abundance in the DEP treatment. Similarly, transcriptome analysis revealed changes in gene expression after oral DEP exposure, but not in the other treatments. The changes are related to metabolism and signal transduction which indicates a general stress response. Taken together, our results suggest potential health effects of DEP exposure on insects, here shown in bumblebees, as gut dysbiosis may increase the susceptibility of bumblebees to pathogens, while a general stress response may lower available energy resources. However, experiments with multiple stressors and on colony level are needed to provide a more comprehensive understanding of the impact of DEPs on insects.
... Moreover, the spread of lactic acid bacteria (LAB) is favored by the activity of adult individuals and the consumption of bee bread and pollen [17]. The microbiome controls the development and migration of pathogens, thus avoiding the induction of harmful systemic immune responses, which can alter the composition of the intestinal microbiome of honeybees [18]. The structure of the bacterial community of microbiota can also be an indicator of the health status of honeybees [19]. ...
Lactic acid bacteria (LAB) are an essential part of the microbiota of the digestive tract of honeybees (Apis mellifera L.). Antagonistic activity of 103 LAB strains (isolates from different environments) against 21 honeybee pathogens/opportunistic pathogens (with agar slab method) was screened. The growth of Paenibacillus genus was inhibited to the most extent. The highest antagonistic activity was demonstrated by Lacticaseibacillus casei 12AN, while the lowest by Apilactobacillus kunkeei DSM 12361, a species naturally inhabiting the honeybee gut. LAB isolated from the honeybee environment demonstrated stronger antagonism against pathogens than collection strains. The antagonistic activity of cell-free supernatants (CFSs) from 24 LAB strains against 7 honeybee pathogens was additionally assessed at physiological pH with the microtitration method. The same was determined for selected CFSs at neutralized pH. CFSs with physiological pH showed significantly stronger antibacterial activity than CFSs with neutralized pH. The results confirmed that the mechanism of antimicrobial activity of LAB is acidification of the environment. The obtained results may, in the future, contribute to a better understanding of the antagonistic properties of LAB and the construction of a probiotic preparation to increase the viability of honeybee colonies.
... Pesticides that disrupt the bee gut microbiota indirectly through host health impairment may require longer periods of exposure to disrupt the microbiome because pesticides require time to accumulate in host tissues and affect host physiology, especially if bees are exposed to low doses, as is likely with Sulf. If a pesticide has strong direct effects on the bee gut microbes, however, it may be able to cause disruption after a shorter exposure duration than pesticides that primarily affect gut microbiota indirectly via impairing host health or altering the gut environment (Daisley et al., 2020). We found rapid impacts of FPF on the gut microbiome of honey bees; direct disruption of the microbiome may therefore be the mode of action of FPF in our study. ...
The gut microbiome plays an important role in bee health and disease. But it can be disrupted by pesticides and in-hive chemicals, putting honey bee health in danger. We used a controlled and fully crossed laboratory experimental design to test the effects of a 10-day period of chronic exposure to field-realistic sublethal concentrations of two nicotinic acetylcholine receptor agonist insecticides (nACHRs), namely flupyradifurone (FPF) and sulfoxaflor (Sulf), and a fungicide, azoxystrobin (Azoxy), individually and in combination, on the survival of individual honey bee workers and the composition of their gut microbiota (fungal and bacterial diversity). Metabarcoding was used to examine the gut microbiota on days 0, 5, and 10 of pesticide exposure to determine how the microbial response varies over time; to do so, the fungal ITS2 fragment and the V4 region of the bacterial 16S rRNA were targeted. We found that FPF has a negative impact on honey bee survival, but interactive (additive or synergistic) effects between either insecticide and the fungicide on honey bee survival were not statistically significant. Pesticide treatments significantly impacted the microbial community composition. The fungicide Azoxy substantially reduced the Shannon diversity of fungi after chronic exposure for 10 days. The relative abundance of the top 10 genera of the bee gut microbiota was also differentially affected by the fungicide, insecticides, and fungicide-insecticide combinations. Gut microbiota dysbiosis was associated with an increase in the relative abundance of opportunistic pathogens such as Serratia spp. (e.g. S. marcescens), which can have devastating consequences for host health such as increased susceptibility to infection and reduced lifespan. Our findings raise concerns about the long-term impact of novel nACHR insecticides, particularly FPF, on pollinator health and recommend a novel methodology for a refined risk assessment that includes the potential effects of agrochemicals on the gut microbiome of bees.
... 35 Alone, chemical exposure can potentially disrupt host interactions with beneficial microbial associates, impair cognition, increase susceptibility to pathogen infection, or even cause death. 36 Additionally, evidence for synergism and increased toxicity among active and/or additive ingredients is rapidly growing, 37,38 spurring further demand for sustainable approaches to disease control that minimize nontarget effects. ...
Disease management is critical to ensuring healthy crop yields and is often targeted at flowers because of their susceptibility to pathogens and direct link to reproduction. Many disease management strategies are unsustainable however because of the potential for pathogens to evolve resistance, or nontarget effects on beneficial insects. Manipulating the floral microbiome holds some promise as a sustainable alternative to chemical means of disease control. In this perspective, we discuss the current state of research concerning floral microbiome assembly and management in agroecosystems as well as future directions aimed at improving the sustainability of disease control and insect-mediated ecosystem services.
... A high abundance of bacteria was found to act as a bodyguard in resistant cultivars, thereby contributing to disease resistance of the host tomato plant (Kwak et al., 2018). Similarly, honeybees have a different core microbiome that influences stress tolerance and host disease resistance (Daisley et al., 2020). In this study, we found that the gut bacterial community between susceptible (RL) and resistant (RH, RR) honeybees was significantly different, while no difference between RH and RR was observed based on two different beta diversity types: the Jaccard index and unweighted UniFrac (Figure 1c,d). ...
The global decline in the population of wild bees has raised serious concerns, as bees are key pollinators that contribute to the sustainability of agriculture. Especially alarming, are the millions of managed bees in Korea that have recently disappeared. Although many abiotic and biotic stresses influence their physiology and behaviour, the causes of these declines have not been thoroughly elucidated. In recent studies, bee gut microbiota was found to play an important role in pathogen defence. We hypothesized that the gut microbiome of honeybees (Apis cerana) resistant (RH and RR) and susceptible (RL) to sacbrood virus disease may differ. To compare the gut bacterial communities of resistant and susceptible bees, alpha diversity and beta diversity analyses were performed. The analysis of alpha diversity revealed that RH had significantly higher Shannon diversity index values than RL. Beta diversity analysis showed that the gut bacterial community of RH was significantly different from that of RL. Four bacterial phyla were identified, and proteobacteria was the most abundant across all samples. Additionally, three operational taxonomic units (OTUs) belonging to Pasteurellales, Burkholderiales, and Pseudomonadales were identified only in RL. In conclusion, the gut bacterial community was significantly different between resistant and susceptible bees, and this difference may contribute to disease resistance.
... Bees are critical pollinators for a wide range of agricultural processes that form global food supplies, but their population has undergone a catastrophic decline over the past decade 108 . Bee microbiome composition can be a useful indicator of the overall colony health status, and these microbial communities can confer colonization resistance against parasites, inhibit entomopathogenic tissue invasion and improve nutrient assimilation from the diet 109 . To improve resistance to infection during active seasons, beekeepers frequently employ antimicrobials as a prophylactic measure to suppress opportunistic bacterial and fungal pathogens. ...
Global biodiversity loss and mass extinction of species are two of the most critical environmental issues the world is currently facing, resulting in the disruption of various ecosystems central to environmental functions and human health. Microbiome-targeted interventions, such as probiotics and microbiome transplants, are emerging as potential options to reverse deterioration of biodiversity and increase the resilience of wildlife and ecosystems. However, the implementation of these interventions is urgently needed. We summarize the current concepts, bottlenecks and ethical aspects encompassing the careful and responsible management of ecosystem resources using the microbiome (termed microbiome stewardship) to rehabilitate organisms and ecosystem functions. We propose a real-world application framework to guide environmental and wildlife probiotic applications. This framework details steps that must be taken in the upscaling process while weighing risks against the high toll of inaction. In doing so, we draw parallels with other aspects of contemporary science moving swiftly in the face of urgent global challenges. Careful and responsible microbiome management is a critical strategy to counter biodiversity loss, but practical and regulatory hurdles must be addressed to maximize its utility.
... The effect of glyphosate on the honey bee Apis mellifera at different stages has extensively been studied. The core microbiota of bees is dominated by eight bacterial species that play a role in insect growth and immunity (Daisley et al. 2020). Glyphosate has been shown to halve relative abundance of four of these species (i.e., Snodgrassella alvi, Bifidobacterium, Lactobacillus Firm-4, and Lactobacillus Firm-5) during the adult stage ). ...
Insects play many important roles in nature due to their diversity, ecological role, and impact on agriculture or human health. They are directly influenced by environmental changes and in particular anthropic activities that constitute an important driver of change in the environmental characteristics. Insects face numerous anthropogenic stressors and have evolved various detoxication mechanisms to survive and/or resist to these compounds. Recent studies highligted the pressure exerted by xenobiotics on insect life-cycle and the important role of insect-associated bacterial microbiota in the insect responses to environmental changes. Stressor exposure can have various impacts on the composition and structure of insect microbiota that in turn may influence insect biology. Moreover, bacterial communities associated with insects can be directly or indirectly involved in detoxification processes with the selection of certain microorganisms capable of degrading xenobiotics. Further studies are needed to assess the role of insect-associated microbiota as key contributor to the xenobiotic metabolism and thus as a driver for insect adaptation to polluted habitats.
... A decrease in these pollinators may indirectly lead to dietary changes and micronutrient deficiency in humans by reducing crop yield (Mahefarisoa et al. 2021). Biotic and abiotic threats affect the microbiota of honeybees (Daisley et al. 2020); therefore, so there is a need to monitor time-and condition-dependent changes in their microbiota. These changes can be observed through routine field analyses, allowing for the identification and stocking of the species for further studies. ...
Honeybee products have been among important consumer products throughout history. Microbiota has attracted attention in recent years due to both their probiotic value and industrial potential. Fructophilic lactic acid bacteria (FLAB), whose field of study has been expanding rapidly in the last 20 years, are among the groups that can be isolated from the bee gut. This study aimed to isolate FLAB from the honeybees of two different geographic regions in Turkey and investigate their probiotic, metabolic and anti-quorum sensing (anti-QS) potential. Metabolic properties were investigated based on fructose toleration and acid and diacetyl production while the probiotic properties of the isolates were determined by examining pH, pepsin, pancreatin resistance, antimicrobial susceptibility, and antimicrobial activity. Anti-QS activities were also evaluated with the Chromobacterium violaceum biosensor strain. Two FLAB members were isolated and identified by the 16S rRNA analysis as Fructobacillus tropaeoli and Apilactobacillus kunkeei, which were found to be tolerant to high fructose, low pH, pepsin, pancreatin, and bile salt environments. Both isolates showed anti-QS activity against the C. violaceum biosensor strain and no diacetyl production. The daily supernatants of the isolates inhibited the growth of Enterococcus faecalis ATCC 29212 among the selected pathogens. The isolates were found resistant to kanamycin, streptomycin, erythromycin, and clindamycin. In the evaluation of the probiotic potential of these species, the negative effect of antibiotics and other chemicals to which honeybees are directly or indirectly exposed draws attention within the scope of the “One Health” approach.
Graphical abstract
... This public health problem is a concern to the authorities, and especially to the beekeeping sector and the scientific community [1][2][3]. The origin of those chemicals comes from veterinary treatments with acaricides, sulfa drugs, antibiotics, etc., necessary to deal with diseases and parasites in bees [4,5]; and from agricultural treatments with pesticides, mainly neonicotinoids [6][7][8][9]. A report by the EFSA (European Food Safety Agency) has confirmed this reality, highlighting the impact of these residues on the health of bees [9], and on that of honey and pollen consumers [10]. ...
As in the case of the food industry in general, there is a global concern about safety and quality in complex food matrices, such as honey, which is driving the demand for fast, sensitive and affordable analytical techniques across the honey-packaging industry. Although excellent techniques such as liquid chromatography-tandem mass spectrometry (LC-MS/MS) are available, these are located in centralized laboratories and are still lacking in speed, simplicity and cost-effectiveness. Here, a new approach is presented where a competitive immunoassay is combined with a novel High Fundamental Frequency Quartz Crystal Microbalance with Dissipation (HFF-QCMD) array biosensor for the simultaneous detection of antibiotics and pesticides in honey. Concretely, thiabendazole and sulfathiazole residues were monitored in spiked honey samples. Results revealed that HFF-QCMD arrays provide a complementary and reliable tool to LC-MS/MS for the analysis of contaminants in these kinds of complex matrices, while avoiding elaborate sample pre-treatment. The good sensitivity achieved (I50 values in the 70–720 µg/kg range) and the short analysis time (60 min for 24 individual assays), together with the ability for multiple analyte detection (24 sensor array) and its cost-effectiveness, pave the way for the implementation of a fast on-line, in situ routine control of potentially hazardous chemical residues in honey.
... The phylum Proteobacteria, Actinobacteriota, and Patescibacteria play important roles in global carbon, nitrogen, sulfur, and iron metabolisms due to their great metabolic diversity (Marín, 2014;Herrmann et al., 2019). The dysbiosis of gut microbial community may affect the host metabolisms and health since most of the gut microbes interacted with gut tissues as a beneficial symbiont (Daisley et al., 2020). In our study, the Procrustes test suggested that the changes in gut microbial community were probably linked to the perturbations in the metabolic profiles of the whole earthworms after exposure to nanoceria (M 2 = 0.263, p = 0.001) (Fig. S8B). ...
The toxic stress caused by nanoceria remains vague owing to the limited efforts scrutinizing its molecular mechanisms. Herein, we investigated the impacts of nanoceria on earthworm Eisenia fetida, at the molecular level using the multiomics-based profiling approaches (transcriptomics, metabolomics, and 16 S rRNA sequencing). Nanoceria (50 and 500 mg/kg) significantly increased the contents of malondialdehyde (MDA), Fe, and K in worms, suggesting oxidative injury and nutrient imbalance. This was corroborated by the transcriptomic and metabolomic analyses. Nanoceria decreased the levels of certain genes and metabolites associated with glycerolipid and glycerophospholipid metabolisms, suggesting the production of reactive oxygen species and subsequent oxidative stress. Additionally, the ABCD3 gene belonging to ABC transporter family was upregulated, facilitating Fe uptake by worms. Moreover, the higher contents of MDA, Fe, and K after exposure were tightly associated with the imbalanced intestinal flora. Specifically, a higher relative abundance of Actinobacteriota and a lower relative abundance of Proteobacteria and Patescibacteria were induced. This study, for the first time, revealed that nanoceria at nonlethal levels caused oxidative stress and nutrient imbalance of earthworms from the perspective of genes, metabolites, and gut microbiome perturbations, and also established links between the gut microbiome and the overall physiological responses of the host.
... The mean rate of parasitism we observed was 23.58% in A. pygamea males (Mlynarek et al., 2015;Nagel et al., 2014). Microclimatic factors such as temperature, rainfall and humidity, and other ecological factors such as food availability, predator pressure and symbiotic microbiota that varies across populations can impact insect immunity and host-parasite interactions (Daisley et al., 2020;Murdock et al., 2012;Myers et al., 2011;Rolff & Siva-Jothy, 2003;Stoks et al., 2006). However, if these factors also impact damselflies-water mite interactions and cause variations of parasitism is yet unknown, . ...
Sexual selection can improve population fitness and purge deleterious mutation from the gene pool by promoting condition‐dependent mate selection. One ecological factor that reduces individual condition is parasitism. Parasitism tends to increase hosts' mutation load and likely indicates inferior host genetic quality. Parasite‐mediated selection, therefore, should favour the mating success of parasite‐resistant individuals over parasitised individuals. We tested this hypothesis in male Agriocnemis pygmaea damselflies, which are parasitised by Arrenurus water mites. We calculated frequency (i.e. the proportion of parasitism) and intensity (i.e. the number of parasites per parasitised individual) of parasitism in free‐flying males and males in copula in seven natural populations. We predicted that males observed mating will be less likely to be parasitised than expected based on the frequency of parasitism in the population. We further predicted that parasite intensity would be lower in males caught in copula than single males. We found that parasitised males were significantly less likely to be found in copula than non‐parasitised males, independent of their occurrence frequency. However, there was no difference in the average parasite load between males captured in copula or free‐flying males. Our study shows that in addition to natural selection, sexual selection is a strong agent against parasitism and implies that it could promote local adaptation to counteract parasite driven extinction risks. Parasite‐mediated selection should favour mating success of parasite resistant individuals over parasitised individuals. We tested this hypothesis in male Agriocnemis pygmaea damselflies, which are parasitised by Arrenurus water mites. We calculated frequency (i.e. the proportion of parasitism), and intensity (i.e. the number of parasites per parasitised individual) of parasitism in free flying males and males in copula in seven natural populations. We predicted that males observed mating will be less likely to be parasitised and at lower intensity than expected based on the frequency and intensity of parasitism in the population. We found that parasitised males were significantly less likely found in copula than non‐parasitised males, However, there was no difference in the average parasite load between mated and unmated males.
... However, the honey bee microbiota is destabilized (dysbiosis) by natural events such as immunosenescence or by various exogenous factors such as climate, diet, nutritional deficiencies, pathogens, pesticides and environmental pollution [151][152][153][154][155][156][157][158]. The functional outcomes of dysbiosis include poor host development, early mortality and increased susceptibility of bees to pathogens [149,152,[159][160][161]. Recent studies provide experimental evidence for a link between nosemosis and dysbiosis in the honey bees' gut [60,[162][163][164][165][166][167][168][169][170][171]. ...
Nosemosis is a disease triggered by the single-celled spore-forming fungi Nosema apis and Nosema ceranae, which can cause extensive colony losses in honey bees (Apis mellifera L.). Fumagillin is an effective antibiotic treatment to control nosemosis, but due to its toxicity, it is currently banned in many countries. Accordingly, in the beekeeping sector, there is a strong demand for alternative ecological methods that can be used for the prevention and therapeutic control of nosemosis in honey bee colonies. Numerous studies have shown that plant extracts, RNA interference (RNAi) and beneficial microbes could provide viable non-antibiotic alternatives. In this article, recent scientific advances in the biocontrol of nosemosis are summarized.
... The gut of adult honey bees is colonized by a particular microbial community of core phylotypes [2][3][4][5] that can be found relatively stable over geographical distances, which is highly affected by the honey bees' eusocial behaviour, colony organization and division of labour [6,7]. Although some fundamental properties of the gut microbiome, i.e. the association of beneficial microbes and the ability of their host to buffer against adverse external impacts and to resist pathogens, are revealed, the causes and consequences of gut dysbiosis are not completely decoded [8][9][10][11]. ...
To avoid potential adverse side effects of chemical plant protection products, microbial pest control products (MPCP) are commonly applied as biological alternatives. This study aimed to evaluate the biosafety of a MPCP with the active organism Bacillus thuringiensis ssp. aizawai (strain: ABTS-1857). An in-hive feeding experiment was performed under field-realistic conditions to examine the effect of B. thuringiensis (B. t.) on brood development and the bacterial abundance of the core gut microbiome ( Bifidobacterium asteroids , Gilliamella apicola , the group of Lactobacillus and Snodgrasella alvi ) in Apis mellifera worker bees. We detected a higher brood termination rate and a non-successful development into worker bees of treated colonies compared to those of the controls. For the gut microbiome, all tested core members showed a significantly lower normalized abundance in bees of the treated colonies than in those of the controls; thus, a general response of the gut microbiome may be assumed. Consequently, colony exposure to B. t. strain ABTS-1857 had a negative effect on brood development under field-realistic conditions and caused dysbiosis of the gut microbiome. Further studies with B. t. –based products, after field-realistic application in bee attractive crops, are needed to evaluate the potential risk of these MPCPs on honey bees.
... Given that gut symbionts are key for the digestive process in bees [26], gut microbiome disruption could also reduce nutritional uptake and energetic budgets, decreasing bee activity levels and willingness to engage with external stimuli [28]. Second, while insects have a haemolymph-brain barrier [29,30], there is virtually no information on whether antibiotics or their metabolites can cross it and, if so, generate neurotoxic impacts sufficient to affect behaviour [31]. Third, bees may avoid foraging on nectar with antibiotic residues. ...
In the past decade, the broadcast-spray application of antibiotics in US crops has increased exponentially in response to bacterial crop pathogens, but little is known about the sublethal impacts on beneficial organisms in agroecosystems. This is concerning given the key roles that microbes play in modulating insect fitness. A growing body of evidence suggests that insect gut microbiomes may play a role in learning and behaviour, which are key for the survival of pollinators and for their pollination efficacy, and which in turn could be disrupted by dietary antibiotic exposure. In the laboratory,
we tested the effects of an upper-limit dietary exposure to streptomycin (200 ppm)—an antibiotic widely used to treat bacterial pathogens in crops— on bumblebee (Bombus impatiens) associative learning, foraging and stimulus avoidance behaviour. We used two operant conditioning assays: a free movement proboscis extension reflex protocol focused on short-term memory formation, and an automated radio-frequency identification tracking system
focused on foraging. We show that upper-limit dietary streptomycin
exposure slowed training, decreased foraging choice accuracy, increased avoidance behaviour and was associated with reduced foraging on sucrose rewarding artificial flowers. This work underscores the need to further study the impacts of antibiotic use on beneficial insects in agricultural systems.
... As discussed above, exposure to glyphosate pesticides damages or eliminates honey bee gut microbes, thereby weakening their immune systems, and increasing their susceptibility to pathogen invasion. As discussed by Daisley et al. (2020), these gut microbes play an essential role in honey bee health. The bees possess a core microbiota that matures during early development and remains relatively stable throughout most of adult life. ...
Western honey bees (Apis mellifera) have been domesticated for their honey, wax, and other products for at least 9000 years, starting in the Middle East. European colonists brought honey bees to North America, starting in the 17th century. Honey bee colonies did extremely well in North America until the mid-1980s, when their populations started to decline. This marked decrease coincided with the accidental introduction of two parasitic mites: the tracheal mite Acarapis and the external mite Varroa. Among the other important factors in the decline are increased exposure to insecticides, herbicides, and fungicides, loss of habitat, and the cross-country transportation of colonies for crop pollination.
... A recent study also indicated that Proteobacteria were the most dominant phylum in gut microbiota at the larvae stage of the lake sturgeon (Abdul Razak and Scribner, 2020). Additionally, the majority of gut microbes interacted with gut tissues as a symbiont with beneficial effects on the host, which were crucial for the early stages (Bates et al., 2006;Daisley et al., 2020). At the genus level, the nTiO 2 exposure increased the relative abundance of Vibrio, which may result in inflammation and tissue damage to the gut (Jia et al., 2019). ...
The environmental stresses could significantly affect the structure and functions of microbial communities colonized in the gut ecosystem. However, little is known about how engineered nanoparticles (ENPs), which have recently become a common pollutant in the environment, affect the gut microbiota across fish development. Based on the high-throughput sequencing of the 16S rRNA gene amplicon, we explored the ecological succession of gut microbiota in zebrafish exposed to nanoparticles for three months. The nanoparticles used herein including titanium dioxide nanoparticles (nTiO2, 100 μg/L), zinc oxide nanoparticles (nZnO, 100 μg/L), and selenium nanoparticles (nSe, 100 μg/L). Our results showed that nanoparticles exposure reduced the alpha diversity of gut microbiota at 73–90 days post-hatching (dph), but showed no significant effects at 14–36 dph. Moreover, nTiO2 significantly (p < 0.05) altered the composition of the gut microbial communities at 73–90 dph (e.g., decreasing abundance of Cetobacterium and Vibrio). Moreover, we found that homogeneous selection was the major process (16.6–57.8%) governing the community succession of gut microbiota. Also, nanoparticles exposure caused topological alterations to microbial networks and led to increased positive interactions to destabilize the gut microbial community. This study reveals the environmental effects of nanoparticles on the ecological succession of gut microbiota across zebrafish development, which provides novel insights to understand the gut microbial responses to ENPs over the development of aquatic animals.
... Vairimorpha ceranae infection may modulate the host's core bacteria by affecting polysaccharide digestion, in addition to the hypothesized immune modulations [46]. We found the pronounced IMO effects of decreasing Lactobacillus spp. ...
Vairimorpha (Nosema) ceranae is the most common eukaryotic gut pathogen in honey bees. Infection is typically chronic but may result in mortality. Gut microbiota is a factor that was recently noted for gut infectious disease development. Interestingly, studies identified positive, instead of negative, associations between core bacteria of honey bee microbiota and V. ceranae infection. To investigate the effects of the positive associations, we added isomaltooligosaccharide (IMO), a prebiotic sugar also found in honey, to enhance the positive associations, and we then investigated the infection and the gut microbiota alterations using qPCR and 16S rRNA gene sequencing. We found that infected bees fed IMO had significantly higher V. ceranae spore counts but lower mortalities. In microbiota comparisons, V. ceranae infections alone significantly enhanced the overall microbiota population in the honey bee hindgut and feces; all monitored core bacteria significantly increased in the quantities but not all in the population ratios. The microbiota alterations caused by the infection were enhanced with IMO, and these alterations were similar to the differences found in bees that naturally have longer lifespans. Although our results did not clarify the causations of the positive associations between the infections and microbiota, the associations seemed to sustain the host survival and benefit the pathogen. Enhancing indigenous gut microbe to control nosema disease may result in an increment of bee populations but not the control of the pathogen. This interaction between the pathogen and microbiota potentially enhances disease transmission and avoids the social immune responses that diseased bees die prematurely to curb the disease from spreading within colonies.
... Missing microbes in bees, as well as systematic depletion of key symbionts, impair bee immunity. Treatment strategies based on microbiota restoration are promising in restoring bee colony health (33). Healthy microbiomes represent the foundations of soil, plant, and animal life in sustainable ecosystems. ...
The COVID-19 pandemic had huge impacts on the global world, with both a negative impact on society and economy but a positive one on nature. But this universal effect resulted in different infection rates from country to country. We analyzed the relationship between the pandemic and ecological, economic, and social conditions. All of these data were collected in 140 countries at six time points. Correlations were studied using univariate and multivariate regression models. The world was interpreted as a single global ecosystem consisting of ecosystem units representing countries. We first studied 140 countries around the world together, and infection rates were related to per capita GDP, Ecological Footprint, median age, urban population, and Biological Capacity, globally. We then ranked the 140 countries according to infection rates. We created four groups with 35 countries each. In the first group of countries, the infection rate was very high and correlated with the Ecological Footprint (consumption) and GDP per capita (production). This group is dominated by developed countries, and their ecological conditions have proved to be particularly significant. In country groups 2, 3, and 4, infection rates were high, medium, and low, respectively, and were mainly related to median age and urban population. In the scientific discussion, we have interpreted why infection rates are very high in developed countries. Sustainable ecosystems are balanced, unlike the ecosystems of developed countries. The resilience and the health of both natural ecosystems and humans are closely linked to the world of microbial communities, the microbiomes of the biosphere. It is clear that both the economy and society need to be in harmony with nature, creating sustainable ecosystems in developed countries as well.
... (1) Given the importance of the honey bee microbiota to the insect's health and immunity, future studies must select strains, including honey bee-derived strains (if appropriate), to fortify deficiencies in the microbiota or to counter a pathogen or disease (Daisley et al. 2020a). ...
The concerns over honey bee health and colony collapse have led to an increased interest in the potential for beneficial bacteria as an intervention. However, the efficacy of this approach is mostly unknown because the application of bacterial adjuncts to hives has not often proceeded by understanding the strains being applied or how they function. This article summarizes the effects reported from published studies (2004–2020) that have experimentally tested the influence of beneficial bacteria, including probiotics, on honey bee immune function, pathogen resistance, or colony productivity. The meta-analysis shows that bacterial intervention can improve bee survival against American foulbrood and Nosema infection, and increase honey yields, but the underlying molecular correlates remain poorly understood. There is some evidence that honey bee–derived bacteria could be superior to exogenous bacterial species, although further evaluation is needed. We advocate for a more organized and transparent approach that includes the rationale for strain choice and delivery, a thorough description of treatment formulations, viable counts and their application to hives, and improved design of experimental field trials to consistently include controls and other features that allow interpretation of results. Successful studies should also be validated for efficacy and reproducibility.
... However, studies indicated that forager honeybees have a "contingent microbiome" dependent mainly on the food they forage [2,10,11]. This carries a danger, because with poor food resources, the microbiota will be inappropriate and non-functioning [62]. Currently, many factors influence bee microbiota e.g.,: monocultures, nutritional stress, pesticide exposure and agrochemicals, many of which exhibit antimicrobial properties, and thus contribute greatly to reductions in honeybee stress tolerance and disease resistance, leading to higher honeybee mortality, and a high rate of colony loss [5,63], pathogens which trigger bee malnutrition [64], changes in the composition of their microelements [65] and yeast content [19]. ...
European Apis mellifera and Asian Apis cerana honeybees are essential crop pollinators. Microbiome studies can provide complex information on health and fitness of these insects in relation to environmental changes, and plant availability. Amplicon sequencing of variable regions of the 16S rRNA from bacteria and the internally transcribed spacer (ITS) regions from fungi and plants allow identification of the metabiome. These methods provide a tool for monitoring otherwise uncultured microbes isolated from the gut of the honeybees. They also help monitor the composition of the gut fungi and, intriguingly, pollen collected by the insect. Here, we present data from amplicon sequencing of the 16S rRNA from bacteria and ITS2 regions from fungi and plants derived from honeybees collected at various time points from anthropogenic landscapes such as urban areas in Poland, UK, Spain, Greece, and Thailand. We have analysed microbial content of honeybee intestine as well as fungi and pollens. Furthermore, isolated DNA was used as the template for screening pathogens: Nosema apis, N. ceranae, N. bombi, tracheal mite (Acarapis woodi), any organism in the parasitic order Trypanosomatida, including Crithidia spp. (i.e., Crithidia mellificae), neogregarines including Mattesia and Apicystis spp. (i.e., Apicistis bombi). We conclude that differences between samples were mainly influenced by the bacteria, plant pollen and fungi, respectively. Moreover, honeybees feeding on a sugar based diet were more prone to fungal pathogens (Nosema ceranae) and neogregarines. In most samples Nosema sp. and neogregarines parasitized the host bee at the same time. A higher load of fungi, and bacteria groups such as Firmicutes (Lactobacillus);
γ
-proteobacteria, Neisseriaceae, and other unidentified bacteria was observed for Nosema ceranae and neogregarine infected honeybees. Healthy honeybees had a higher load of plant pollen, and bacteria groups such as: Orbales, Gilliamella, Snodgrassella, and Enterobacteriaceae. Finally, the period when honeybees switch to the winter generation (longer-lived forager honeybees) is the most sensitive to diet perturbations, and hence pathogen attack, for the whole beekeeping season. It is possible that evolutionary adaptation of bees fails to benefit them in the modern anthropomorphised environment.
RESUMO: Com o passar dos anos, o franco desenvolvimento e evolução do sistema alimentar tem garantido o acesso à alimentação básica em todo o planeta e a apicultura tem exercido papel-chave neste processo. Por conta da polinização de plantações agrícolas e também do fornecimento de produtos derivados do mel, as abelhas têm sido cada vez mais estudadas na área de sistemas agroindustriais para que se garanta a sobrevivência e produtividade de suas colônias. Atualmente um dos principais desafios para garantir a saúde das colônias é o enfrentamento do ectoparasita Varroa destructor. Este ácaro tem sido o principal vilão para as abelhas melíferas ocidentais por conta de suas características parasitárias, seu ciclo de reprodução e principalmente por ser vetor de transmissão de diversas doenças. Os apicultores utilizam diversas técnicas e práticas para redução ou erradicação de ácaros, como métodos apícolas biotécnicas, acaricidas sintéticos e acaricidas orgânicos ou suaves, e novos desafios surgem de acordo com a abordagem escolhida para o tratamento. São frequentes os relatos de contaminação do mel, exposição das abelhas a acaricidas em doses subletais, evolução genética dos ácaros a determinados acaricidas, entre outras adversidades. A continuidade de estudos de campo e laboratoriais são determinantes para que as práticas dos apicultores quanto ao enfrentamento ao Varroa seja efetivo e não produza efeitos colaterais a longo ou a curto prazo. Palavras-chave: Varroa, ácaro, acaricida, ectoparasita. ABSTRACT: Over the years, the frank development and evolution of the food system has guaranteed access to basic food across the planet and beekeeping has played a key role in this process. Because of the pollination of agricultural crops and also the supply of products derived from honey, bees have been increasingly studied in the area of agro-industrial systems to ensure the survival and productivity of their colonies. Currently, one of the main challenges to ensure the health of colonies is facing the ectoparasite Varroa destructor. This mite has been the main villain for western honey bees because of its parasitic characteristics, its reproduction cycle and mainly because it is a transmission vector of several diseases. Beekeepers use various techniques and practices to reduce or eradicate mites, such as biotechnical beekeeping methods, synthetic acaricides and organic or mild acaricides, and new challenges arise according to the chosen approach for treatment. There are frequent reports of contamination of honey, exposure of bees to acaricides in sublethal doses, genetic evolution of mites to certain acaricides, among other adversities. The continuity of field and laboratory studies are crucial for the practices of beekeepers in terms of coping with Varroa to be effective and not produce side effects in the long or short term.
Stingless bees play a crucial role in the environment and agriculture as they are effective pollinators. Furthermore, they can produce various products that can be exploited economically, such as propolis and honey. Despite their economic value, the knowledge of microbial community of stingless bees, and their roles on the bees' health, especially in Thailand, are in its infancy. This study aimed to investigate the composition and the functions of bacterial community associated with Tetragonula pagdeni stingless bees using culture-independent and culture-dependent approaches with emphasis on lactic acid bacteria. The culture-independent results showed that the dominant bacterial phyla were Firmicutes, Proteobacteria and Actinobacteria. The most abundant families were Lactobacillaceae and Halomonadaceae. Functional prediction indicated that the prevalent functions of bacterial communities were chemoheterotrophy and fermentation. In addition, the bacterial community might be able to biosynthesize amino acid and antimicrobial compounds. Further isolation and characterization resulted in isolates that belonged to the dominant taxa of the community and possessed potentially beneficial metabolic activity. This suggested that they are parts of the nutrient acquisition and host defense bacterial functional groups in Thai commercial stingless bees.
To understand life in all its varieties, we must undertake to understand our cells and, most particularly, acknowledge that all cells are problem-solving, communicating, self-referential agents. As a result, our traditional conceptions of intelligence and problem-solving must be thoroughly redefined. This radical new approach explains precisely why our human choices are centered within the same cellular rules that enable our cells to seamlessly sustain our lives. While the partnership between our cells and our microbes has largely been thought of as “host” and “guest,” the reciprocal interactions between essential living fractions in holobionts is so intimate that we should regard ourselves as a consensual 'we'. Exploring the extent of the deep integration of our cellular networks yields profound insights about ourselves, our health and well-being, our social systems, and our permanent relationship with the planet and the cosmos.
Besides representing one of the most relevant threats of fungal origin to human and animal health, the genus Aspergillus includes opportunistic pathogens which may infect bees (Hymenoptera, Apoidea) in all developmental stages. At least 30 different species of Aspergillus have been isolated from managed and wild bees. Some efficient behavioral responses (e.g., diseased brood removal) exerted by bees negatively affect the chance to diagnose the pathology, and may contribute to the underestimation of aspergillosis importance in beekeeping. On the other hand, bee immune responses may be affected by biotic and abiotic stresses and suffer from the loose co-evolutionary relationships with Aspergillus pathogenic strains. However, if not pathogenic, these hive mycobiota components can prove to be beneficial to bees, by affecting the interaction with other pathogens and parasites and by detoxifying xenobiotics. The pathogenic aptitude of Aspergillus spp. likely derives from the combined action of toxins and hydrolytic enzymes, whose effects on bees have been largely overlooked until recently. Variation in the production of these virulence factors has been observed among strains, even belonging to the same species. Toxigenic and non-toxigenic strains/species may co-exist in a homeostatic equilibrium which is susceptible to be perturbed by several external factors, leading to mutualistic/antagonistic switch in the relationships between Aspergillus and bees.
Chronic antibiotic exposure impacts host health through changes to the microbiome. The detrimental effects of antibiotic perturbation on microbiome structure and function after one host generation of exposure have been well-studied, but less is understood about multigenerational effects of antibiotic exposure and subsequent recovery. In this study, we examined microbiome composition and host fitness across five generations of exposure to antibiotics in the model zooplankton host Daphnia magna. By utilizing a split-brood design where half of the offspring from antibiotic-exposed parents were allowed to recover and half were maintained in antibiotics, we examined recovery and resilience of the microbiome. Unexpectedly, we discovered that isolation of single host individuals across generations exerted a strong effect on microbiome composition, with microbiome diversity decreasing over generations regardless of treatment while host body size and cumulative reproduction increased across generations. Though antibiotics did cause substantial changes to microbiome composition within a generation, recovery generally occurred in one generation regardless of the number of prior generations spent in antibiotics. Our results demonstrate that isolation of individual hosts leads to stochastic extinction of less abundant taxa in the microbiome, suggesting that these taxa are likely maintained via transmission in host populations.
Background:
While several agricultural fungicides are known to directly affect invertebrate pests, including aphids, the mechanisms involved are often unknown. One hypothesis is that fungicides with antibacterial activity suppress bacterial endosymbionts present in aphids which are important for aphid survival. Endosymbiont-related effects are expected to be transgenerational, given that these bacteria are maternally inherited. Here, we test for these associations using three fungicides (chlorothalonil, pyraclostrobin and trifloxystrobin) against the bird cherry-oat aphid, Rhopalosiphum padi, using a microinjected strain that carried both the primary endosymbiont Buchnera and the secondary endosymbiont Rickettsiella.
Results:
We show that the fungicide chlorothalonil did not cause an immediate effect on aphid survival, whereas both strobilurin fungicides (pyraclostrobin and trifloxystrobin) decreased survival after 48 h exposure. However, chlorothalonil substantially reduced the lifespan and fecundity of the F1 generation. Trifloxystrobin also reduced the lifespan and fecundity of F1 offspring, however, pyraclostrobin did not affect these traits. None of the fungicides consistently altered the density of Buchnera or Rickettsiella in whole aphids.
Conclusions:
Our results suggest fungicides have sublethal impacts on R. padi that are not fully realised until the generation after exposure, and these sublethal impacts are not associated with the density of endosymbionts harboured by R. padi. However, we cannot rule out other effects of fungicides on endosymbionts that might influence fitness, like changes in their tissue distribution. We discuss these results within the context of fungicidal effects on aphid suppression across generations and point to potential field applications. This article is protected by copyright. All rights reserved.
Microbiome breeding is a new artificial selection technique that seeks to change the genetic composition of microbiomes in order to benefit plant or animal hosts. Recent experimental and theoretical analyses have shown that microbiome breeding is possible whenever microbiome-encoded genetic factors affect host traits (e.g., health) and microbiomes are transmissible between hosts with sufficient fidelity, such as during natural microbiome transmission between individuals of social animals, or during experimental microbiome transplanting between plants. To address misunderstandings that stymie microbiome-breeding programs, we (i) clarify and visualize the corresponding elements of microbiome selection and standard selection; (ii) elucidate the eco-evolutionary processes underlying microbiome selection within a quantitative genetic framework to summarize practical guidelines that optimize microbiome breeding; and (iii) characterize the kinds of host species most amenable to microbiome breeding.
Protective symbionts can defend hosts from parasites through several mechanisms, from direct interference to modulating host immunity, with subsequent effects on host and parasite fitness. While research on symbiont-mediated immune priming (SMIP) has focused on ecological impacts and agriculturally important organisms, the evolutionary implications of SMIP are less clear. Here, we review recent advances made in elucidating the ecological and molecular mechanisms by which SMIP occurs. We draw on current works to discuss the potential for this phenomenon to drive host, parasite, and symbiont evolution. We also suggest approaches that can be used to address questions regarding the impact of immune priming on host-microbe dynamics and population structures. Finally, due to the transient nature of some symbionts involved in SMIP, we discuss what it means to be a protective symbiont from ecological and evolutionary perspectives and how such interactions can affect long-term persistence of the symbiosis.
Honey bees (Apis mellifera) are agriculturally important pollinators. Over the past decades, significant losses of wild and domestic bees have been reported in many parts of the world. Several biotic and abiotic factors, such as change in land use over time, intensive land management, use of pesticides, climate change, beekeeper’s management practices, lack of forage (nectar and pollen), and infection by parasites and pathogens, negatively affect the honey bee’s well-being and survival. The gut microbiota is important for honey bee growth and development, immune function, protection against pathogen invasion; moreover, a well-balanced microbiota is fundamental to support honey bee health and vigor. In fact, the structure of the bee’s intestinal bacterial community can become an indicator of the honey bee’s health status. Lactic acid bacteria are normal inhabitants of the gastrointestinal tract of many insects, and their presence in the honey bee intestinal tract has been consistently reported in the literature. In the first section of this review, recent scientific advances in the use of LABs as probiotic supplements in the diet of honey bees are summarized and discussed. The second section discusses some of the mechanisms by which LABs carry out their antimicrobial activity against pathogens. Afterward, individual paragraphs are dedicated to Chalkbrood, American foulbrood, European foulbrood, Nosemosis, and Varroosis as well as to the potentiality of LABs for their biological control.
Social bee gut microbiotas play key roles in host health and performance. Worryingly, a growing body of literature shows that pesticide exposure can disturb these microbiotas. Most studies examine changes in taxonomic composition in Western honey bee (Apis mellifera) gut microbiotas caused by insecticide exposure. Core bee gut microbiota taxa shift in abundance after exposure but are rarely eliminated, with declines in Bifidobacteriales and Lactobacillus near melliventris abundance being the most common shifts. Pesticide concentration, exposure duration, season and concurrent stressors all influence whether and how bee gut microbiotas are disturbed. Also, the mechanism of disturbance-i.e. whether a pesticide directly affects microbial growth or indirectly affects the microbiota by altering host health-likely affects disturbance consistency. Despite growing interest in this topic, important questions remain unanswered. Specifically, metabolic shifts in bee gut microbiotas remain largely uninvestigated, as do effects of pesticide-disturbed gut microbiotas on bee host performance. Furthermore, few bee species have been studied other than A. mellifera, and few herbicides and fungicides have been examined. We call for these knowledge gaps to be addressed so that we may obtain a comprehensive picture of how pesticides alter bee gut microbiotas, and of the functional consequences of these changes.
Background:
Chlorothalonil is a non-systemic fungicide, and it is one of the most widely detected pesticides in bee hives. The effect of chlorothalonil on the survival, weight, and gut microbiota of immature Apis mellifera L. reared in vitro was studied.
Results:
Larvae were fed 1, 2, 4, 8 and 16 μg/mL chlorothalonil and compared with larvae fed the negative control (diet without any additives), positive control (45 mg/L dimethoate), and solvent control (2% acetone). Compared with the control groups, the survival of the 2, 4, 8 and 16 μg/mL chlorothalonil treatments was significantly reduced. The no-observed-adverse-effect concentration (NOAEC) of chlorothalonil was 1 μg/mL. Chlorothalonil had no significant effect on larval weight. The gut bacterial community composition of newly emerged bees was determined by PacBio 16S rDNA gene sequencing. LEFSe analysis showed that Pseudomonadales and Burkholderiales were affected by exposure to chlorothalonil.
Conclusion:
Chlorothalonil reduced the survival of honey bee larvae and altered the gut microbiota of newly emerged bees. The risk of pesticides to honey bees is related to their toxicity and exposure dose.
This work investigated host-microbiome interactions during a crucial developmental stage—the transition from larvae to adults, which is a challenge to both the insect host and its microbiome. Using the honey bee as a tractable model system, we showed that microbiome transfer after emergence overrides any variation in the larval microbiome in honey bees, indicating that larval and adult microbiome stages are effectively decoupled.
Honeybee symbionts, predominantly bacteria, play important roles in honeybee health, nutrition, and pathogen protection, thereby supporting colony health. On the other hand, fungi are often considered indicators of poor bee health, and honeybee microbiome studies generally exclude fungi and yeasts. We hypothesized that yeasts may be an important aspect of early honeybee biology, and if yeasts provide a mutual benefit to their hosts, then honeybees could provide a refuge during metamorphosis to ensure the presence of yeasts at emergence. We surveyed for yeast and fungi during pupal development and metamorphosis in worker bees using fungal-specific quantitative polymerase chain reaction (qPCR), next-generation sequencing, and standard microbiological culturing. On the basis of yeast presence in three distinct apiaries and multiple developmental stages, we conclude that yeasts can survive through metamorphosis and in naïve worker bees, albeit at relatively low levels. In comparison, known bacterial mutualists, like Gilliamella and Snodgrassella, were generally not found in pre-eclosed adult bees. Whether yeasts are actively retained as an important part of the bee microbiota or are passively propagating in the colony remains unknown. Our demonstration of the constancy of yeasts throughout development provides a framework to further understand the honeybee microbiota.
Animal hosts have initiated myriad symbiotic associations with microorganisms and often have maintained these symbioses for millions of years, spanning drastic changes in ecological conditions and lifestyles. The establishment and persistence of these relationships require genetic innovations on the parts of both symbionts and hosts. The nature of symbiont innovations depends on their genetic population structure, categorized here as open, closed or mixed. These categories reflect modes of inter-host transmission that result in distinct genomic features, or genomic syndromes, in symbionts. Although less studied, hosts also innovate in order to preserve and control symbiotic partnerships. New capabilities to sequence host-associated microbial communities and to experimentally manipulate both hosts and symbionts are providing unprecedented insights into how genetic innovations arise under different symbiont population structures and how these innovations function to support symbiotic relationships.
Medonosna pčela (Apis mellifera) izrazito je osjetljiva na varoozu, koju izaziva grinja Varroa destructor. Ako se ne zaštite od varooze, pčelinje zajednice u pravilu propadaju nakon jedne do tri godine. Zaštita pčelinjih zajednica kemijskim sredstvima sve je manje učinkovita zbog rezistentnosti grinja i nepoželjna je zbog zaostajanja aktivnih tvari u pčelinjim proizvodima. Cilj rada je pregledom literature istražiti potencijal te prednosti i nedostatke primjene bioloških agensa u suzbijanju varoe. Prikazani su biološki aspekti grinje Varroa destructor u interakciji sa pčelom kao domaćinom i bioagensima te utjecaj fizikalnih uvjeta u košnici na učinkovitost bioagensa. Posljednja se dva desetljeća u suzbijanju varoe i sličnih organizama istražuju korisni člankonšci, entomopatogene nematode, entomopatogene gljive i bakterije. S obzirom na visoku učinkovitost u suzbijanju varoe i sigurnost za pčele, entomopatogene gljive iz rodova Metarhizium i Beauveria, entomopatogene bakterije Bacillus thuringiensis te simbiotske bakterije entomopatogenih nematoda potencijalni su bioagensi. U budućim istraživanjima treba standardizirati metode ocjene djelovanja bioagensa na varou i pčelinju zajednicu i tehnološki prilagoditi potencijalne bioagense fizikalnim uvjetima u košnici, uzimajući u obzir sigurnost pčela, pčelara i kvalitetu meda.
Background:
Chronic antibiotic exposure impacts host health through changes to the microbiome, increasing disease risk and reducing the functional repertoire of community members. The detrimental effects of antibiotic perturbation on microbiome structure and function after one host generation of exposure have been well-studied. However, much less is understood about the multigenerational effects of antibiotic exposure and how the microbiome may recover across host generations.
Results:
In this study, we examined microbiome composition and host fitness across five generations of exposure to a suite of three antibiotics in the model zooplankton host Daphnia magna. By utilizing a split-brood design where half of the offspring from antibiotic-exposed parents were allowed to recover and half were maintained in antibiotics, we aimed to examine recovery and resilience of the microbiome. Unexpectedly, we discovered that experimental isolation of single host individuals across generations also exerted a strong effect on microbiome composition, with composition becoming less diverse over generations regardless of treatment. Simultaneously, Daphnia magna body size and cumulative reproduction increased across generations while survival decreased. Though antibiotics did cause substantial changes to microbiome composition, the microbiome generally became similar to the no antibiotic control treatment within one generation of recovery no matter how many prior generations were spent in antibiotics.
Conclusions:
Contrary to results found in vertebrate systems, Daphnia magna microbiome composition recovers quickly after antibiotic exposure. However, our results suggest that the isolation of individual hosts leads to the stochastic extinction of rare taxa in the microbiome, indicating that these taxa are likely maintained via transmission in host populations rather than intrinsic mechanisms. This may explain the intriguing result that microbiome diversity loss increased host fitness.
COVID-19 pandemic had huge impacts on the global world, with both a negative impact on society and economy, but a positive one on nature. But this universal effect resulted in different infection rates from country to country. We analyzed the relationship between the pandemic and ecological, economic, and social characteristics. All of these data were collected in 140 countries at 6 time points. Correlations were studied using univariate and multivariate regression models.
The world was interpreted as a single global ecosystem consisting of ecosystem units representing countries. We first studied 140 countries around the world together, and infection rates were related to per capita GDP, Ecological Footprint, median age, urban population, and Biological Capacity, globally. We then ranked 140 countries by infection rate and created 4 equal groups, each with 35 countries. In the first group, the infection rate was very high and was related to the Ecological Footprint (consumption) and GDP per capita (production). This group is dominated by developed countries and their ecological characteristics have proven to be particularly significant. In groups 2, 3, and 4, infection rates were high, moderate, and low, and were primarily associated with median age and urban population.
In the scientific discussion, we have interpreted why infection is high in developed countries. Sustainable ecosystems are balanced, unlike the ecosystems of developed countries. According to science, the resilience and health of both natural ecosystems and humans are closely linked to the world of microbial communities. Our results suggest that both the economy and society need to be in harmony with nature, creating sustainable ecosystems in developed countries as well.
Honeybees are essential pollinators of many agricultural crops and wild plants. However, the number of managed bee colonies has declined in some regions of the world over the last few decades, probably caused by a combination of factors including parasites, pathogens and pesticides. Exposure to these diverse biotic and abiotic stressors is likely to trigger immune responses and stress pathways that affect the health of individual honeybees and hence their contribution to colony survival. We therefore investigated the effects of an orally administered bacterial pathogen ( Pseudomonas entomophila ) and low-dose xenobiotic pesticides on honeybee survival and intestinal immune responses. We observed stressor-dependent effects on the mean lifespan, along with the induction of genes encoding the antimicrobial peptide abaecin and the detoxification factor cytochrome P450 monooxygenase CYP9E2. The pesticides also triggered the immediate induction of a nitric oxide synthase gene followed by the delayed upregulation of catalase, which was not observed in response to the pathogen. Honeybees therefore appear to produce nitric oxide as a specific defense response when exposed to xenobiotic stimuli. The immunity-related and stress-response genes we tested may provide useful stressor-dependent markers for ecotoxicological assessment in honeybee colonies.
Honey bees are important pollinators of many major crops and add billions of dollars annually to the US economy through their services. Recent declines in the health of the honey bee have startled researchers and lay people alike as honey bees are agricultures most important pollinator. One factor that may influence colony health is the microbial community. Although honey bee worker guts have a characteristic community of bee-specific microbes, the honey bee queen digestive tracts are colonized predominantly by a single acetic acid bacterium tentatively named Candidatus Parasaccharibacter apium. This bacterium is related to flower-associated microbes such as Saccharibacter floricola, and initial phylogenetic analyses placed it as sister to these environmental bacteria. We used a combination of phylogenetic and sequence identity methods to better resolve evolutionary relationships among P. apium, strains in the genus Saccharibacter, and strains in the closely related genus Bombella. Interestingly, measures of genome-wide average nucleotide identity and aligned fraction, coupled with phylogenetic placement, indicate that many strains labeled as P. apium and Saccharibacter sp. are all the same species as Bombella apis. We propose reclassifying these strains as Bombella apis and outline the data supporting that classification below.
There is growing number of studies demonstrating a close relationship between insect gut microbiota and insecticide resistance. However, the contribution of the honey bee gut microbiota to host detoxification ability has yet to be investigated. In order to address this question, we compared the expression of cytochrome P450s (P450s) genes between gut microbiota deficient (GD) workers and conventional gut community (CV) workers and compared the mortality rates and the pesticide residue levels of GD and CV workers treated with thiacloprid or tau‐fluvalinate. Our results showed that gut microbiota promotes the expression of P450 enzymes in the midgut, and the mortality rate and pesticide residue levels of GD workers are significantly higher than those of CV workers. Further comparisons between tetracycline‐treated workers and untreated workers demonstrated that antibiotic‐induced gut dysbiosis leads to attenuated expression of P450s in the midgut. The co‐treatment of antibiotics and pesticides leads to reduced survival rate and a significantly higher amount of pesticide residues in honey bees. Taken together, our results demonstrated that honey bee gut symbiont could contribute to bee health through the modification of the host xenobiotics detoxification pathways and revealed a potential negative impact of antibiotics to honey bee detoxification ability and health. Our results demonstrated that honey bee gut symbiont could contribute to bee health through the modification of the host xenobiotics detoxification pathways and revealed a potential negative impact of antibiotics to honey bee detoxification ability and health.
Lactobacillus salivarius A3iob was administered to productive colonies belonging to commercial apiaries of small beekeepers (around 30–50 hives each one), from four departments of the province of Jujuy (Argentina): Yala, Tilquiza, El Carmen, and Los Alisos. The incidence of Varroa destructor and Nosema spp., before and after winter, was monitored during 2 years of study (2014–2015). Depending on the geographical location of each apiary and the application time, a monthly dose of the bacteria (10⁵ CFU/mL) reduced the levels of varroasis between 50 and 80%. Interestingly, L. salivarius A3iob cells remitted the percentage of the mites to undetectable values in an apiary treated with flumethrin (at Yala, Yungas region).
On the other hand, the spore levels of Nosema spp. in the lactobacilli-treated colonies also depended on the apiary and the year of application, but a significant decrease was mainly observed in the post-winter period. However, at Rivera (El Carmen’s department), no significant changes were detected in both parameters.
These results obtained after 2 years of work suggest that delivering L. salivarius A3iob cells to the bee colonies can become a new eco-friendly tool to cooperate with the control of these bees’ pests.
Managed populations of the European honey bee (Apis mellifera) support the production of a global food supply. This important role in modern agriculture has rendered honey bees vulnerable to the noxious effects of anthropogenic stressors such as pesticides. Although the deleterious outcomes of lethal pesticide exposure on honey bee health and performance are apparent, the ominous role of sublethal pesticide exposure is an emerging concern as well. Here, we use a data harvesting approach to better understand the toxicological effects of pesticide exposure across the honey bee life cycle. Through compiling adult- and larval-specific median lethal dose (LD50) values from 93 published data sources, LD50 estimates for insecticides, herbicides, acaricides, and fungicides are highly variable across studies, especially for herbicides and fungicides, which are underrepresented in the meta-data set. Alongside major discrepancies in these reported values, further examination of the compiled data suggested that LD50 may not be an ideal metric for honey bee risk assessment. We also discuss how sublethal effects of pesticide exposure, which are not typically measured in LD50 studies, can diminish honey bee reproduction, immunity, cognition, and overall physiological functioning, leading to suboptimal honey bee performance and population reduction. In consideration of actionable solutions to mitigate the effects of sublethal pesticide exposure, we have identified the potential for probiotic supplementation as a promising strategy that can be easily incorporated alongside current agricultural infrastructure and apicultural management practices. Probiotic supplementation is regularly employed in apiculture but the potential for evidence-based targeted approaches has not yet been fully explored within a formal toxicological context. We discuss the benefits, practical considerations, and limitations for the use and delivery of probiotics to hives. Ultimately, by subverting the sublethal effects of pesticides we can help improve the long-term survival of these critical pollinators.
Although the use of probiotic bacteria in invertebrates is still rare, scientists have begun to look into their usage in honey bees. The probiotic preparation, based on the autochthonous strain Lactobacillus brevis B50 Biocenol™ (CCM 8618), which was isolated from the digestive tracts of healthy bees, was applied to the bee colonies in the form of a pollen suspension. Its influence on the immune response was determined by monitoring the expression of genes encoding immunologically important molecules in the honey bee intestines. Changes in the intestinal microbiota composition were also studied. The results showed that the probiotic Lact. brevis B50, on a pollen carrier, significantly increased the expression of genes encoding antimicrobial peptides (abaecin, defensin-1) as well as pattern recognition receptors (toll-like receptor, peptidoglycan recognition proteins). Gene expression for the other tested molecules included in Toll and Imd signaling pathways (dorsal, cactus, kenny, relish) significantly changed during the experiment. The positive effect on intestinal microbiota was manifested mainly by a significant increase in the ratio of lactic acid bacteria to enterobacteria. These findings confirm the potential of the tested probiotic preparation to enhance immunity in bee colonies and thus increase their resistance to infectious diseases and stress conditions.
Adult honeybees harbor a specialized gut microbiota of relatively low complexity. While seasonal differences in community composition have been reported, previous studies have focused on compositional changes rather than differences in absolute bacterial loads. Moreover, little is known about the gut microbiota of winter bees, which live much longer than bees during the foraging season, and which are critical for colony survival. We quantified seven core members of the bee gut microbiota in a single colony over 2 years and characterized the community composition in 14 colonies during summer and winter. Our data show that total bacterial loads substantially differ between foragers, nurses, and winter bees. Long-lived winter bees had the highest bacterial loads and the lowest community α-diversity, with a characteristic shift toward high levels of Bartonella and Commensalibacter, and a reduction of opportunistic colonizers. Using gnotobiotic bee experiments, we show that diet is a major contributor to the observed differences in bacterial loads. Overall, our study reveals that the gut microbiota of winter bees is remarkably different from foragers and nurses. Considering the importance of winter bees for colony survival, future work should focus on the role of the gut microbiota in winter bee health and disease.
Bees acquire carbohydrates from nectar and lipids; and amino acids from pollen, which also contains polysaccharides including cellulose, hemicellulose, and pectin. These potential energy sources could be degraded and fermented through microbial enzymatic activity, resulting in short chain fatty acids available to hosts. However, the contributions of individual microbiota members to polysaccharide digestion have remained unclear. Through analysis of bacterial isolate genomes and a metagenome of the honey bee gut microbiota, we identify that Bifidobacterium and Gilliamella are the principal degraders of hemicellulose and pectin. Both Bifidobacterium and Gilliamella show extensive strain-level diversity in gene repertoires linked to polysaccharide digestion. Strains from honey bees possess more such genes than strains from bumble bees. In Bifidobacterium , genes encoding carbohydrate-active enzymes are colocated within loci devoted to polysaccharide utilization, as in Bacteroides from the human gut. Carbohydrate-active enzyme-encoding gene expressions are up-regulated in response to particular hemicelluloses both in vitro and in vivo. Metabolomic analyses document that bees experimentally colonized by different strains generate distinctive gut metabolomic profiles, with enrichment for specific monosaccharides, corresponding to predictions from genomic data. The other 3 core gut species clusters ( Snodgrassella and 2 Lactobacillus clusters) possess few or no genes for polysaccharide digestion. Together, these findings indicate that strain composition within individual hosts determines the metabolic capabilities and potentially affects host nutrition. Furthermore, the niche specialization revealed by our study may promote overall community stability in the gut microbiomes of bees.
American foulbrood (AFB) is a highly virulent disease afflicting honey bees (Apis mellifera). The causative organism, Paenibacillus larvae, attacks honey bee brood and renders entire hives dysfunctional during active disease states, but more commonly resides in hives asymptomatically as inactive spores that elude even vigilant beekeepers. The mechanism of this pathogenic transition is not fully understood, and no cure exists for AFB. Here, we evaluated how hive supplementation with probiotic lactobacilli (delivered through a nutrient patty; BioPatty) affected colony resistance towards a naturally occurring AFB outbreak. Results demonstrated a significantly lower pathogen load and proteolytic activity of honey bee larvae from BioPatty-treated hives. Interestingly, a distinctive shift in the microbiota composition of adult nurse bees occurred irrespective of treatment group during the monitoring period, but only vehicle-supplemented nurse bees exhibited higher P. larvae loads. In vitro experiments utilizing laboratory-reared honey bee larvae showed Lactobacillus plantarum Lp39, Lactobacillus rhamnosus GR-1, and Lactobacillus kunkeei BR-1 (contained in the BioPatty) could reduce pathogen load, upregulate expression of key immune genes, and improve survival during P. larvae infection. These findings suggest the usage of a lactobacilli-containing hive supplement, which is practical and affordable for beekeepers, may be effective for reducing enzootic pathogen-related hive losses.
Sublethal exposure to certain pesticides (e.g., neonicotinoid insecticides) is suspected to contribute to honey bee ( Apis mellifera ) population decline in North America. Neonicotinoids are known to interfere with immune pathways in the gut of insects, but the underlying mechanisms remain elusive. We used a Drosophila melanogaster model to understand how imidacloprid (a common neonicotinoid) interferes with two innate immune pathways—Duox and Imd. We found that imidacloprid dysregulates these pathways to reduce hydrogen peroxide production, ultimately leading to a dysbiotic shift in the gut microbiota. Intriguingly, we found that presupplementation with probiotic bacteria could mitigate the harmful effects of imidacloprid. Thus, these observations uncover a novel mechanism of pesticide-induced immunosuppression that exploits the interconnectedness of two important insect immune pathways.
The use of pesticides to ensure global food security is the most important pest control strategy in modern agriculture but causes extensive soil pollution. This pollution involves potential risks to human health and ecosystems. In addition to soil animal growth, the adverse impact of pesticides on the gut microbiomes of nontarget soil fauna remains largely unknown. Here, the effect of the fungicide azoxystrobin (AZ) on soil and the gut microbiota of soil animals (Enchytraeus crypticus) was studied. The tested concentrations of AZ altered the bacterial community in the soil and E. crypticus gut and were slightly toxic with respect to E. crypticus adult mortality and reproduction. The most abundant bacterial phylum, Proteobacteria, significantly increased in response to the 2 and 5 mg/kg AZ treatments, which implied a disordered unhealthy gut bacterial community. Furthermore, bacterial community analysis between the soil and gut showed that the main effect of AZ on the gut microbiota was directly through AZ, not soil microbiota. In addition, AZ exposure significantly enhanced the number and total abundance of antibiotic resistance genes (ARGs) in the E. crypticus gut; these genes may enter the soil food web to affect higher trophic levels and cause a more serious ecological risk. Our study reported the effect of pesticides on the gut of soil animals and on the enrichment of ARGs as global emerging contaminants, revealing unknown potential impacts of fungicides on ecosystem services and sustainable food production.
The previously demonstrated antagonistic effects of honeybee-derived bacterial microbiota on the infectivity and pathogenicity of P. larvae in laboratory bioassays have identified a possible new approach to AFB control. However, honeybee colonies are complex superorganisms where social immune defenses play a major role in resistance against disease at the colony level. Few studies have investigated the effect of beneficial microorganisms on bee diseases at the colony level. Effects observed at the individual bee level do not necessarily translate into similar effects at the colony level. This study partially fills this gap by showing that, unlike at the individual level, hbs-LAB supplements did not affect AFB symptoms at the colony level. The inference is that the mechanisms regulating the honeybee microbial dynamics within a colony are too strong to manipulate positively through supplemental feeding of live hbs-LAB and that new potential remedies identified through laboratory research have to be tested thoroughly in situ , in colonies.
The honeybee (Apis mellifera) has to cope with multiple environmental stressors, especially pesticides. Among those, the herbicide glyphosate and its main metabolite, the aminomethylphosphonic acid (AMPA), are among the most abundant and ubiquitous contaminant in the environment. Through the foraging and storing of contaminated resources, honeybees are exposed to these xenobiotics. As ingested glyphosate and AMPA are directly in contact with the honeybee gut microbiota, we used quantitative PCR to test whether they could induce significant changes in the relative abundance of the major gut bacterial taxa. Glyphosate induced a strong decrease in Snodgrassella alvi, a partial decrease of a Gilliamella apicola and an increase in Lactobacillus spp. abundances. In vitro, glyphosate reduced the growth of S. alvi and G. apicola but not Lactobacillus kunkeei. Although being no bee killer, we confirmed that glyphosate can have sublethal effects on the honeybee microbiota. To test whether such imbalanced microbiota could favor pathogen development, honeybees were exposed to glyphosate and to spores of the intestinal parasite Nosema ceranae. Glyphosate did not significantly enhance the effect of the parasite infection. Concerning AMPA, while it could reduce the growth of G. apicola in vitro, it did not induce any significant change in the honeybee microbiota, suggesting that glyphosate is the active component modifying the gut communities.
The honey bee, Apis mellifera, pollinates a wide variety of essential crops in numerous ecosystems around the world but faces many modern challenges. Among these, the microsporidian pathogen Nosema ceranae is one of the primary detriments to honey bee health. Nosema infects the honey bee gut, which harbors a highly specific, coevolved microbiota heavily involved in bee immune function and nutrition. Here, we extend previous work investigating interactions between the honey bee gut microbiome and N. ceranae by studying experimentally infected bees that were returned to their colonies and sampled 5, 10, and 21 days post-infection. We measured Nosema load with quantitative PCR and characterized microbiota with 16S rRNA gene amplicon sequencing. We found significant colony level variation in infection levels, and subtle differences between the microbiota of colonies with high infection levels versus those with low infection levels. Two exact sequence variants of Gilliamella, a core gut symbiont that has previously been associated with gut dysbiosis, were significantly more abundant in bees from colonies with high Nosema loads versus those with low Nosema loads. These bacteria deserve further study to determine if they facilitate more intense infection by Nosema ceranae.
The gut microbiota plays an essential role in the health of bees. To elucidate the effect of feed and Nosema ceranae infection on the gut microbiota of honey bee (Apis cerana), we used 16S rRNA sequencing to survey the gut microbiota of honey bee workers fed with sugar water or beebread and inoculated with or without N. ceranae. The gut microbiota of A. cerana is dominated by Serratia, Snodgrassella, and Lactobacillus genera. The overall gut microbiota diversity was show to be significantly differential by feeding type. N. ceranae infection significantly affects the gut microbiota only in bees fed with sugar water. Higher abundances of Lactobacillus, Gluconacetobacter, and Snodgrassella and lower abundances of Serratia were found in bees fed with beebread than in those fed with sugar water. N. ceranae infection led to a higher abundance of Snodgrassella and a lower abundance of Serratia in sugar-fed bees. Imputed bacterial Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways showed the significant metagenomics functional differences by feeding and N. ceranae infections. Furthermore, A. cerana workers fed with sugar water showed lower N. ceranae spore loads but higher mortality than those fed with beebread. The cumulative mortality was strongly positive correlated (rho=0.61) with the changes of overall microbiota dissimilarities by N. ceranae infection. Both feeding types and N. ceranae infection significantly affect the gut microbiota in A. cerana workers. Beebread not only provides better nutrition but also helps establish a more stable gut microbiota and therefore protects bees in response to N. ceranae infection.
Significance
Increased mortality of honey bee colonies has been attributed to several factors but is not fully understood. The herbicide glyphosate is expected to be innocuous to animals, including bees, because it targets an enzyme only found in plants and microorganisms. However, bees rely on a specialized gut microbiota that benefits growth and provides defense against pathogens. Most bee gut bacteria contain the enzyme targeted by glyphosate, but vary in whether they possess susceptible versions and, correspondingly, in tolerance to glyphosate. Exposing bees to glyphosate alters the bee gut community and increases susceptibility to infection by opportunistic pathogens. Understanding how glyphosate impacts bee gut symbionts and bee health will help elucidate a possible role of this chemical in colony decline.
We investigated the importance of protein nutrition for honey bee immunity. Different protein diets (monofloral pollen of Helianthus spp., Sinapis spp., Asparagus spp., Castanea spp., a mixture of the four different pollen and the pollen substitute FeedbeeTM) were fed to honey bees in cages ad libitum. After 18 days of feeding, apidaecin 1 isoforms concentration in the thorax were measured using nanoflow liquid chromatography coupled with mass spectrometry. Expression levels of genes, coding for apidaecins and abaecin in the abdomen were determined using quantitative PCR. The results indicate that protein-containing nutrition in adult worker honey bees can trigger certain metabolic responses. Bees without dietary protein showed lower apidaecin 1 isoforms concentrations. The significantly lowest concentration of apidaecin 1 isoforms was found in the group that was fed no pollen diet when compared to Asparagus, Castanea, Helianthus, and Sinapis pollen or the pollen supplement FeedBeeTM. Expression levels of the respective genes were also affected by the protein diets and different expression levels of these two antimicrobial peptides were found. Positive correlation between concentration and gene expression of apidaecins was found. The significance of feeding bees with different protein diets, as well as the importance of pollen nutrition for honey bee immunity is demonstrated.
Background
As the use and diversity of probiotic products expands, the choice of an appropriate type of probiotic is challenging for both medical care professionals and the public alike. Two vital factors in choosing the appropriate probiotic are often ignored, namely, the probiotic strain-specificity and disease-specificity for efficacy. Reviews and meta-analyses often pool together different types of probiotics, resulting in misleading conclusions of efficacy.MethodsA systematic review of the literature (1970–2017) assessing strain-specific and disease-specific probiotic efficacy was conducted. Trials were included for probiotics with an identifiable strain (either single strain or mixtures of strains) that had at least two randomized, controlled trials for each type of disease indication. The goal was to determine if probiotic strains have strain and/or disease-specific efficacy.ResultsWe included 228 trials and found evidence for both strain specificity and disease specificity for the efficacy of specific probiotic strains. Significant efficacy evidence was found for 7 (70%) of probiotic strain(s) among four preventive indications and 11 (65%) probiotic strain(s) among five treatment indications. Strain-specific efficacy for preventing adult antibiotic-associated diarrhea was clearly demonstrated within the Lactobacillus species [e.g., by the mixture of Lactobacillus acidophilus CL1285, Lactobacillus casei LBC80R, and Lactobacillus rhamnosus CLR2 (Bio-K+®), by L. casei DN114001 (Actimel®) and by Lactobacillus reuteri 55730], while other Lactobacillus strains did not show efficacy. Significant disease-specific variations in efficacy was demonstrated by L. rhamnosus GG and Saccharomyces boulardii CNCM I-745, as well as other probiotic strains.Conclusion
Strong evidence was found supporting the hypothesis that the efficacy of probiotics is both strain-specific and disease-specific. Clinical guidelines and meta-analyses need to recognize the importance of reporting outcomes by both specific strain(s) of probiotics and the type of disease. The clinical relevance of these findings indicates that health-care providers need to take these two factors into consideration when recommending the appropriate probiotic for their patient.
A few commonly used non-antibiotic drugs have recently been associated with changes in gut microbiome composition, but the extent of this phenomenon is unknown. Here, we screened more than 1,000 marketed drugs against 40 representative gut bacterial strains, and found that 24% of the drugs with human targets, including members of all therapeutic classes, inhibited the growth of at least one strain in vitro. Particular classes, such as the chemically diverse antipsychotics, were overrepresented in this group. The effects of human-targeted drugs on gut bacteria are reflected on their antibiotic-like side effects in humans and are concordant with existing human cohort studies. Susceptibility to antibiotics and human-targeted drugs correlates across bacterial species, suggesting common resistance mechanisms, which we verified for some drugs. The potential risk of non-antibiotics promoting antibiotic resistance warrants further exploration. Our results provide a resource for future research on drug-microbiome interactions, opening new paths for side effect control and drug repurposing, and broadening our view of antibiotic resistance.
Nosema ceranae is an intracellular microsporidian parasite of the Asian honey bee Apis cerana and the European honey bee Apis mellifera. Until relatively recently, A. mellifera honey bees were naïve to N. ceranae infection. Symptoms of nosemosis, or Nosema disease, in the infected hosts include immunosuppression, damage to gut epithelium, nutrient and energetic stress, precocious foraging and reduced longevity of infected bees. Links remain unclear between immunosuppression, the symptoms of nutrient and energetic stress, and precocious foraging behavior of hosts. To clarify physiological connections, we inoculated newly emerged A. mellifera adult workers with N. ceranae spores, and over 21 days post inoculation (21 days pi), gauged infection intensity and quantified expression of genes representing two innate immune pathways, Toll and Imd. Additionally, we measured each host's whole-body protein, lipids, carbohydrates and quantified respirometric and activity levels. Results show sustained suppression of genes of both humorally regulated immune response pathways after 6 days pi. At 7 days pi, elevated protein levels of infected bees may reflect synthesis of antimicrobial peptides from an initial immune response, but the lack of protein gain compared with uninfected bees at 14 days pi may represent low de novo protein synthesis. Carbohydrate data do not indicate that hosts experience severe metabolic stress related to this nutrient. At 14 days pi infected honey bees show high respirometric and activity levels, and corresponding lipid loss, suggesting lipids may be used as fuel for increased metabolic demands resulting from infection. Accelerated lipid loss during nurse honey bee behavioral development can have cascading effects on downstream physiology that may lead to precocious foraging, which is a major factor driving colony collapse.
The purpose of this article is to reveal the role of the lactic acid bacteria (LAB) in the beebread transformation/preservation, biochemical properties of 25 honeybee endogenous LAB strains, particularly: antifungal, proteolytic, and amylolytic activities putatively expressed in the beebread environment have been studied. Seventeen fungal strains isolated from beebread samples were identified and checked for their ability to grow on simulated beebread substrate (SBS) and then used to study mycotic propagation in the presence of LAB. Fungal strains identified as Aspergillus niger (Po1), Candida sp. (BB01), and Z. rouxii (BB02) were able to grow on SBS. Their growth was partly inhibited when co-cultured with the endogenous honeybee LAB strains studied. No proteolytic or amylolytic activities of the studied LAB were detected using pollen, casein starch based media as substrates. These findings suggest that some honeybee LAB symbionts are involved in maintaining a safe microbiological state in the host honeybee colonies by inhibiting beebread mycotic contaminations, starch, and protein predigestion in beebread by LAB is less probable. Honeybee endogenous LAB use pollen as a growth substrate and in the same time restricts fungal propagation, thus showing host beneficial action preserving larval food. This study also can have an impact on development of novel methods of pollen preservation and its processing as a food ingredient.
The gut microbiome plays a key role in animal health, and perturbing it can have detrimental effects. One major source of perturbation to microbiomes, in humans and human-associated animals, is exposure to antibiotics. Most studies of how antibiotics affect the microbiome have used amplicon sequencing of highly conserved 16S rRNA sequences, as in a recent study showing that antibiotic treatment severely alters the species-level composition of the honeybee gut microbiome. But because the standard 16S rRNA-based methods cannot resolve closely related strains, strain-level changes could not be evaluated. To address this gap, we used amplicon sequencing of protein-coding genes to assess effects of antibiotics on fine-scale genetic diversity of the honeybee gut microbiota. We followed the population dynamics of alleles within two dominant core species of the bee gut community, Gilliamella apicola and Snodgrassella alvi, following antibiotic perturbation. Whereas we observed a large reduction of genetic diversity in G. apicola, S. alvi diversity was mostly unaffected. The reduction of G. apicola diversity accompanied an increase in the frequency of several alleles, suggesting resistance to antibiotic treatment. We find that antibiotic perturbation can cause major shifts in diversity, and that the extent of these shifts can vary substantially across species. Thus, antibiotics impact not only species composition, but also allelic diversity within species, potentially affecting hosts if variants with particular functions are reduced or eliminated. Overall, we show that amplicon sequencing of protein-coding genes, without clustering into operational taxonomic units (OTUs), provides an accurate picture of the fine-scale dynamics of microbial communities over time. This article is protected by copyright. All rights reserved.
It has become increasingly clear that gut bacteria play vital roles in the development, nutrition, immunity, and overall fitness of their eukaryotic hosts. We conducted the present study to investigate the effects of gut microbiota disruption on the honey bee’s immune responses to infection by the microsporidian parasite Nosema ceranae. Newly emerged adult workers were collected and divided into four groups: Group I—no treatment; Group II—inoculated with N. ceranae, Group III—antibiotic treatment, and Group IV—antibiotic treatment after inoculation with N. ceranae. Our study showed that Nosema infection did not cause obvious disruption of the gut bacterial community as there was no significant difference in the density and composition of gut bacteria between Group I and Group II. However, the elimination of gut bacteria by antibiotic (Groups III and IV) negatively impacted the functioning of the honey bees’ immune system as evidenced by the expression of genes encoding antimicrobial peptides abaecin, defensin1, and hymenoptaecin that showed the following ranking: Group I > Group II > Group III > Group IV. In addition, significantly higher Nosema levels were observed in Group IV than in Group II, suggesting that eliminating gut bacteria weakened immune function and made honey bees more susceptible to Nosema infection. Based on Group IV having displayed the highest mortality rate among the four experimental groups indicates that antibiotic treatment in combination with stress, associated with Nosema infection, significantly and negatively impacts honey bee survival. The present study adds new evidence that antibiotic treatment not only leads to the complex problem of antibiotic resistance but can impact honey bee disease resistance. Further studies aimed at specific components of the gut bacterial community will provide new insights into the roles of specific bacteria and possibly new approaches to improving bee health.