Mild chronic exposure to pesticides alters physiological markers of honey bee health without perturbing the core gut microbiota

Comparative toxicity of oral exposure to paraquat: Survival rates and gene expression in two honey bees species; Apis mellifera and Apis cerana

Honey bees provide vital pollination services to agricultural crops and wild plants worldwide. Unfortunately, the misuse and overuse of pesticides in agricultural production have led to an increase in incidents harming honey bees in recent years. Among the commonly utilized bee species in beekeeping are Apis cerana and Apis mellifera, with wild A. cerana populations widely dispersed in forests, contributing substantially to ecosystem balance. Yet, the impact of paraquat, a toxic herbicide, on A. cerana remains largely unexplored. This study aims to address this gap by examining acute exposure endpoints based on mortality represented by median lethal doses (LD50 values) of paraquat, survival rates, and gene expression patterns between the A. cerana and A. mellifera. The findings revealed that A. cerana exhibits greater sensitivity to paraquat compared to A. mellifera. The acute oral LD50 values for A. cerana were 5.85, 1.74, and 1.21 μg/bee at 24, 48, and 72 h, respectively, whereas the corresponding values for A. mellifera were 104.00, 11.00, and 6.41 μg/bee. Further, the study demonstrated significant upregulation of the detoxification (antioxidative) enzymes SOD1, CAT, and LLDH-X2 in both A. mellifera and A. cerana following exposure to the lethal dose of paraquat. However, SOD2 expression was notably downregulated in both species, indicating potential mitochondrial damage. These findings suggest that while honey bees initiate activate defense mechanisms against oxidative damage, paraquat exposure may still impair mitochondrial function. Paraquat was found to be moderately toxic to A. mellifera but highly toxic to A. cerana, indicating the importance of screening multiple bee species when assessing the risks of chemical exposure. This research provides a rare comparative analysis of chemical stress effects on morbidity and gene expression in two different honey bee species, establishing a foundational framework for risk assessment and the regulation of herbicide risks to pollinating insects.

Cyto and Genoprotective Potential of Tannic Acid Against Cadmium and Nickel Co-exposure Induced Hepato-Renal Toxicity in BALB/c Mice

Tannic acid (TA) is a metal chelating polyphenol that plays a crucial role in metal detoxification, but its modulatory role in co-exposure of these heavy metals' exposure needs to be explored. Cadmium (Cd) and nickel (Ni) are inorganic hazardous chemicals in the environment. Humans are prone to be exposed to the co-exposure of Cd and Ni, but the toxicological interactions of these metals are poorly defined. Present study was undertaken to study the preventive role of TA in Cd-Ni co-exposure-evoked hepato-renal toxicity in BALB/c mice. In the current investigation, increased oxidative stress in metal intoxicated groups was confirmed by elevated peroxidation of the lipids and significant lowering of endogenous antioxidant enzymes. Altered hepato-renal serum markers, DNA fragmentation, and histological alterations were also detected in the metal-treated groups. Present study revealed that Cd is a stronger toxicant than Ni and when co-exposure was administered, additive, sub-additive, and detrimental effects were observed. Prophylactic treatment with TA significantly reinstated the levels of lipid peroxidation (LPO), non-enzymatic, and enzymatic antioxidants. Moreover, it also restored the serum biomarker levels, DNA damage, and histoarchitecture of the given tissues. TA due to its metal chelating and anti-oxidative properties exhibited cyto- and genoprotective potential against Cd-Ni co-exposure-induced hepatic and renal injury.

Recent advances in the toxicological effects of difenoconazole: A focus on toxic mechanisms in fish and mammals

The toxicological study of pesticides at sub-lethal and environment-relevant concentrations has become increasingly crucial for human and environmental health. Toxic mechanisms of agrochemicals contribute to discovering green pesticides, assessing the hazards of pesticides comprehensively, and supporting legitimate regulatory decisions. However, the toxicological effects of difenoconazole are not yet fully understood despite being frequently detected in fruits, vegetables, waters, and soils and posing hazards to humans and the environment. This lack of knowledge could lead to flawed risk assessment and administrative oversight. Thus, the review aimed to provide some investigation perspectives for clarifying the toxicological effects of difenoconazole by synthesizing the toxic data of difenoconazole on various organisms, such as bees, Daphnia magna, fish, earthworms, mammals, and plants and summarizing the toxicological mechanisms of difenoconazole, especially in fish and mammals from peer-reviewed publications. Evidence revealed that difenoconazole caused multiple toxicological effects, including developmental toxicity, reproductive toxicity, endocrine disruption effects, neurotoxicity, and transgenerational toxicity. The toxic mechanisms involved in metabolic disturbance, oxidative stress, inflammation, apoptosis, and autophagy by activating reactive oxygen species-mediated signaling pathways and mitochondrial apoptosis routes, disturbing amino acids, lipid, and nucleotide metabolism, and regulating gene transcription and expression in mammals and fish. Based on the review, further studies better focus on the toxic differences of difenoconazole stereoisomers, the toxicological effects of transformation products of difenoconazole, and the mechanism of action of difenoconazole on sex-specific endocrine disruption effects, intestinal damage, and gut dysbacteriosis for its hazard assessment and management synthetically.

Glyphosate effects on growth and biofilm formation in bee gut symbionts and diverse associated bacteria

Biofilm formation is a common adaptation enabling bacteria to thrive in various environments and withstand external pressures. In the context of host-microbe interactions, biofilms play vital roles in establishing microbiomes associated with animals and plants and are used by opportunistic microbes to facilitate survival within hosts. Investigating biofilm dynamics, composition, and responses to environmental stressors is crucial for understanding microbial community assembly and biofilm regulation in health and disease. In this study, we explore in vivo colonization and in vitro biofilm formation abilities of core members of the honey bee (Apis mellifera) gut microbiota. Additionally, we assess the impact of glyphosate, a widely used herbicide with antimicrobial properties, and a glyphosate-based herbicide formulation on growth and biofilm formation in bee gut symbionts as well as in other biofilm-forming bacteria associated with diverse animals and plants. Our results demonstrate that several strains of core bee gut bacterial species can colonize the bee gut, which probably depends on their ability to form biofilms. Furthermore, glyphosate exposure elicits variable effects on bacterial growth and biofilm formation. In some instances, the effects correlate with the bacteria's ability to encode a susceptible or tolerant version of the enzyme inhibited by glyphosate in the shikimate pathway. However, in other instances, no such correlation is observed. Testing the herbicide formulation further complicates comparisons, as results often diverge from glyphosate exposure alone, suggesting that co-formulants influence bacterial growth and biofilm formation. These findings highlight the nuanced impacts of environmental stressors on microbial biofilms, with both ecological and host health-related implications.

IMPORTANCE

Biofilms are essential for microbial communities to establish and thrive in diverse environments. In the honey bee gut, the core microbiota member Snodgrassella alvi forms biofilms, potentially aiding the establishment of other members and promoting interactions with the host. In this study, we show that specific strains of other core members, including Bifidobacterium, Bombilactobacillus, Gilliamella, and Lactobacillus, also form biofilms in vitro. We then examine the impact of glyphosate, a widely used herbicide that can disrupt the bee microbiota, on bacterial growth and biofilm formation. Our findings demonstrate the diverse effects of glyphosate on biofilm formation, ranging from inhibition to enhancement, reflecting observations in other beneficial or pathogenic bacteria associated with animals and plants. Thus, glyphosate exposure may influence bacterial growth and biofilm formation, potentially shaping microbial establishment on host surfaces and impacting health outcomes.

Effects of glyphosate exposure on intestinal microbiota, metabolism and microstructure: a systematic review

Glyphosate is the most commercialized herbicide in Brazil and worldwide, and this has become a worrying scenario in recent years. In 2015 glyphosate was classified as potentially carcinogenic by the World Health Organization, which opened avenues for numerous debates about its safe use regarding non-target species' health, including humans. This review aimed to observe the impacts of glyphosate and its formulations on the gut microbiota, as well as on the gut microstructure and animal metabolism. A systematic review was conducted based on the PRISMA recommendations, and the search for original articles was performed in Pubmed/Medline, Scopus and Web of Science databases. The risk of bias in the studies was assessed using the SYRCLE strategy. Our findings revealed that glyphosate and its formulations are able to induce intestinal dysbiosis by altering bacterial metabolism, intestinal permeability, and mucus secretion, as well as causing damage to the microvilli and the intestinal lumen. Additionally, immunological, enzymatic and genetic changes were also observed in the animal models. At the metabolic level, damage was observed in lipid and energy metabolism, the circulatory system, cofactor and vitamin metabolism, and replication, repair, and translation processes. In this context, we pointed out that the studies revealed that these alterations, caused by glyphosate-based herbicides, can lead to intestinal and systemic diseases, such as Crohn's disease and Alzheimer's disease.

Prospects of probiotics in beekeeping: a review for sustainable approach to boost honeybee health

Honeybees are vital for global crop pollination, making indispensable contributions to agricultural productivity. However, these vital insects are currently facing escalating colony losses on a global scale, primarily attributed to parasitic and pathogenic attacks. The prevalent response to combat these infections may involve the use of antibiotics. Nevertheless, the application of antibiotics raises concerns regarding potential adverse effects such as antibiotic resistance and imbalances in the gut microbiota of bees. In response to these challenges, this study reviews the utilization of a probiotic-supplemented pollen substitute diet to promote honeybee gut health, enhance immunity, and overall well-being. We systematically explore various probiotic strains and their impacts on critical parameters, including survival rate, colony strength, honey and royal jelly production, and the immune response of bees. By doing so, we emphasize the significance of maintaining a balanced gut microbial community in honeybees. The review also scrutinizes the factors influencing the gut microbial communities of bees, elucidates the consequences of dysbiosis, and evaluates the potential of probiotics to mitigate these challenges. Additionally, it delineates different delivery mechanisms for probiotic supplementation and elucidates their positive effects on diverse health parameters of honeybees. Given the alarming decline in honeybee populations and the consequential threat to global food security, this study provides valuable insights into sustainable practices aimed at supporting honeybee populations and enhancing agricultural productivity.

Enhancing knowledge of chemical exposures and fate in honey bee hives: Insights from colony structure and interactions

Honey bees are unintentionally exposed to a wide range of chemicals through various routes in their natural environment, yet research on the cumulative effects of multi-chemical and sublethal exposures on important caste members, including the queen bee and brood, is still in its infancy. The hive's social structure and food-sharing (trophallaxis) practices are important aspects to consider when identifying primary and secondary exposure pathways for residential hive members and possible chemical reservoirs within the colony. Secondary exposures may also occur through chemical transfer (maternal offloading) to the brood and by contact through possible chemical diffusion from wax cells to all hive members. The lack of research on peer-to-peer exposures to contaminants and their metabolites may be in part due to the limitations in sensitive analytical techniques for monitoring chemical fate and dispersion. Combined application of automated honey bee monitoring and modern chemical trace analysis techniques could offer rapid progress in quantifying chemical transfer and accumulation within the hive environment and developing effective mitigation strategies for toxic chemical co-exposures. To enhance the understanding of chemical fate and toxicity within the entire colony, it is crucial to consider both the intricate interactions among hive members and the potential synergistic effects arising from combinations of chemical and their metabolites.

The honeybee microbiota and its impact on health and disease

Honeybees (Apis mellifera) are key pollinators that support global agriculture and are long-established models for developmental and behavioural research. Recently, they have emerged as models for studying gut microbial communities. Earlier research established that hindguts of adult worker bees harbour a conserved set of host-restricted bacterial species, each showing extensive strain variation. These bacteria can be cultured axenically and introduced to gnotobiotic hosts, and some have basic genetic tools available. In this Review, we explore the most recent research showing how the microbiota establishes itself in the gut and impacts bee biology and health. Microbiota members occupy specific niches within the gut where they interact with each other and the host. They engage in cross-feeding and antagonistic interactions, which likely contribute to the stability of the community and prevent pathogen invasion. An intact gut microbiota provides protection against diverse pathogens and parasites and contributes to the processing of refractory components of the pollen coat and dietary toxins. Absence or disruption of the microbiota results in altered expression of genes that underlie immunity, metabolism, behaviour and development. In the field, such disruption by agrochemicals may negatively impact bees. These findings demonstrate a key developmental and protective role of the microbiota, with broad implications for bee health.

Metagenomic analysis of the honey bee queen microbiome reveals low bacterial diversity and Caudoviricetes phages

In eusocial insects, the health of the queens-the colony founders and sole reproductive females-is a primary determinant for colony success. Queen failure in the honey bee Apis mellifera, for example, is a major concern of beekeepers who annually suffer colony losses, necessitating a greater knowledge of queen health. Several studies on the microbiome of honey bees have characterized its diversity and shown its importance for the health of worker bees, the female non-reproductive caste. However, the microbiome of workers differs from that of queens, which, in comparison, is still poorly studied. Thus, direct investigations of the queen microbiome are required to understand colony-level microbiome assembly, functional roles, and evolution. Here, we used metagenomics to comprehensively characterize the honey bee queen microbiome. Comparing samples from different geographic locations and breeder sources, we show that the microbiome of queens is mostly shaped by the environment experienced since early life and is predicted to play roles in the breakdown of the diet and protection from pathogens and xenobiotics. We also reveal that the microbiome of queens comprises only four candidate core bacterial species, Apilactobacillus kunkeei, Lactobacillus apis, Bombella apis, and Commensalibacter sp. Interestingly, in addition to bacteria, we show that bacteriophages infect the queen microbiome, for which Lactobacillaceae are predicted to be the main reservoirs. Together, our results provide the basis to understand the honey bee colony microbiome assemblage, can guide improvements in queen-rearing processes, and highlight the importance of considering bacteriophages for queen microbiome health and microbiome homeostasis in eusocial insects.IMPORTANCEThe queen caste plays a central role in colony success in eusocial insects, as queens lay eggs and regulate colony behavior and development. Queen failure can cause colonies to collapse, which is one of the major concerns of beekeepers. Thus, understanding the biology behind the queen's health is a pressing issue. Previous studies have shown that the bee microbiome plays an important role in worker bee health, but little is known about the queen microbiome and its function in vivo. Here, we characterized the queen microbiome, identifying for the first time the present species and their putative functions. We show that the queen microbiome has predicted nutritional and protective roles in queen association and comprises only four consistently present bacterial species. Additionally, we bring to attention the spread of phages in the queen microbiome, which increased in abundance in failing queens and may impact the fate of the colony.

Synthetic Communities of Gut Microbes for Basic Research and Translational Approaches in Animal Health and Nutrition

Microbes and animals have a symbiotic relationship that greatly influences nutrient uptake and animal health. This relationship can be studied using selections of microbes termed synthetic communities, or SynComs. SynComs are used in many different animal hosts, including agricultural animals, to investigate microbial interactions with nutrients and how these affect animal health. The most common host focuses for SynComs are currently mouse and human, from basic mechanistic research through to translational disease models and live biotherapeutic products (LBPs) as treatments. We discuss SynComs used in basic research models and findings that relate to human and animal health and nutrition. Translational use cases of SynComs are discussed, followed by LBPs, especially within the context of agriculture. SynComs still face challenges, such as standardization for reproducibility and contamination risks. However, the future of SynComs is hopeful, especially in the areas of genome-guided SynCom design and custom SynCom-based treatments.

Phytochemicals, Probiotics, Recombinant Proteins: Enzymatic Remedies to Pesticide Poisonings in Bees

The ongoing global decline of bees threatens biodiversity and food safety as both wild plants and crops rely on bee pollination to produce viable progeny or high-quality products in high yields. Pesticide exposure is a major driving force for the decline, yet pesticide use remains unreconciled with bee conservation since studies demonstrate that bees continue to be heavily exposed to and threatened by pesticides in crops and natural habitats. Pharmaceutical methods, including the administration of phytochemicals, probiotics (beneficial bacteria), and recombinant proteins (enzymes) with detoxification functions, show promise as potential solutions to mitigate pesticide poisonings. We discuss how these new methods can be appropriately developed and applied in agriculture from bee biology and ecotoxicology perspectives. As countless phytochemicals, probiotics, and recombinant proteins exist, this Perspective will provide suggestive guidance to accelerate the development of new techniques by directing research and resources toward promising candidates. Furthermore, we discuss practical limitations of the new methods mentioned above in realistic field applications and propose recommendations to overcome these limitations. This Perspective builds a framework to allow researchers to use new detoxification techniques more efficiently in order to mitigate the harmful impacts of pesticides on bees.

Combined effect of a neonicotinoid insecticide and a fungicide on honeybee gut epithelium and microbiota, adult survival, colony strength and foraging preferences

Fungicides, insecticides and herbicides are widely used in agriculture to counteract pathogens and pests. Several of these molecules are toxic to non-target organisms such as pollinators and their lethal dose can be lowered if applied as a mixture. They can cause large and unpredictable problems, spanning from behavioural changes to alterations in the gut. The present work aimed at understanding the synergistic effects on honeybees of a combined in-hive exposure to sub-lethal doses of the insecticide thiacloprid and the fungicide penconazole. A multidisciplinary approach was used: honeybee mortality upon exposure was initially tested in cage, and the colonies development monitored. Morphological and ultrastructural analyses via light and transmission electron microscopy were carried out on the gut of larvae and forager honeybees. Moreover, the main pollen foraging sources and the fungal gut microbiota were studied using Next Generation Sequencing; the gut core bacterial taxa were quantified via qPCR. The mortality test showed a negative effect on honeybee survival when exposed to agrochemicals and their mixture in cage but not confirmed at colony level. Microscopy analyses on the gut epithelium indicated no appreciable morphological changes in larvae, newly emerged and forager honeybees exposed in field to the agrochemicals. Nevertheless, the gut microbial profile showed a reduction of Bombilactobacillus and an increase of Lactobacillus and total fungi upon mixture application. Finally, we highlighted for the first time a significant honeybee diet change after pesticide exposure: penconazole, alone or in mixture, significantly altered the pollen foraging preference, with honeybees preferring Hedera pollen. Overall, our in-hive results showed no severe effects upon administration of sublethal doses of thiacloprid and penconazole but indicate a change in honeybees foraging preference. A possible explanation can be that the different nutritional profile of the pollen may offer better recovery chances to honeybees.

Impact of glyphosate (RoundupTM) on the composition and functionality of the gut microbiome

Glyphosate, the active ingredient in the broad-spectrum herbicide RoundupTM, has been a topic of discussion for decades due to contradictory reports of the effect of glyphosate on human health. Glyphosate inhibits the enzyme 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) of the shikimic pathway producing aromatic amino acids in plants, a mechanism that suggests that the herbicide would not affect humans as this pathway is not found in mammals. However, numerous studies have implicated glyphosate exposure in the manifestation of a variety of disorders in the human body. This review specifically outlines the potential effect of glyphosate exposure on the composition and functionality of the gut microbiome. Evidence has been building behind the hypothesis that the composition of each individual gut microbiota significantly impacts health. For this reason, the potential of glyphosate to inhibit the growth of beneficial microbes in the gut or alter their functionality is an important topic that warrants further consideration.

Wild bee and pollen microbiomes across an urban-rural divide

Wild pollinators and their microbiota are sensitive to land use changes from anthropogenic activities that disrupt landscape and environmental features. As urbanization and agriculture affect bee habitats, human-led disturbances are driving changes in bee microbiomes, potentially leading to dysbiosis detrimental to bee fitness. This study examines the bacterial, fungal, and plant compositions of the small carpenter bee, Ceratina calcarata, and its pollen provisions across an urban-rural divide. We performed metabarcoding of C. calcarata and provisions in Toronto by targeting the 16S rRNA, ITS, and rbcL regions. Despite similar plant composition and diversity across bees and their provisions, there was a greater microbial diversity in pollen provisions than in bees. By characterizing the differences in land use, climate, and pesticide residues that differentiate urban and rural landscapes, we find that urban areas support elevated levels of microbial diversity and more complex networks between microbes and plants than rural areas. However, urban areas may lead to lower relative abundances of known beneficial symbionts and increased levels of pathogens, such as Ascosphaera and Alternaria fungi. Further, rural pollen provisions indicate elevated pesticide residues that may dysregulate symbiosis. As anthropogenic activities continue to alter land use, ever changing environments threaten microbiota crucial in maintaining bee health.

The Bacterial Gq Signal Transduction Inhibitor FR900359 Impairs Soil-Associated Nematodes

The cyclic depsipeptide FR900359 (FR) is derived from the soil bacterium Chromobacterium vaccinii and known to bind Gq proteins of mammals and insects, thereby abolishing the signal transduction of their Gq protein-coupled receptors, a process that leads to severe physiological consequences. Due to their highly conserved structure, Gq family of proteins are a superior ecological target for FR producing organisms, resulting in a defense towards a broad range of harmful organisms. Here, we focus on the question whether bacteria like C. vaccinii are important factors in soil in that their secondary metabolites impair, e.g., plant harming organisms like nematodes. We prove that the Gq inhibitor FR is produced under soil-like conditions. Furthermore, FR inhibits heterologously expressed Gαq proteins of the nematodes Caenorhabditis elegans and Heterodera schachtii in the micromolar range. Additionally, in vivo experiments with C. elegans and the plant parasitic cyst nematode H. schachtii demonstrated that FR reduces locomotion of C. elegans and H. schachtii. Finally, egg-laying of C. elegans and hatching of juvenile stage 2 of H. schachtii from its cysts is inhibited by FR, suggesting that FR might reduce nematode dispersion and proliferation. This study supports the idea that C. vaccinii and its excreted metabolome in the soil might contribute to an ecological equilibrium, maintaining and establishing the successful growth of plants.

Low Levels of Hive Stress Are Associated with Decreased Honey Activity and Changes to the Gut Microbiome of Resident Honey Bees

Honey bees (Apis mellifera) face increasing threats to their health, particularly from the degradation of floral resources and chronic pesticide exposure. The properties of honey and the bee gut microbiome are known to both affect and be affected by bee health. Using samples from healthy hives and hives showing signs of stress from a single apiary with access to the same floral resources, we profiled the antimicrobial activity and chemical properties of honey and determined the bacterial and fungal microbiome of the bee gut and the hive environment. We found honey from healthy hives was significantly more active than honey from stressed hives, with increased phenolics and antioxidant content linked to higher antimicrobial activity. The bacterial microbiome was more diverse in stressed hives, suggesting they may have less capacity to exclude potential pathogens. Finally, bees from healthy and stressed hives had significant differences in core and opportunistically pathogenic taxa in gut samples. Our results emphasize the need for understanding and proactively managing bee health. IMPORTANCE Honey bees serve as pollinators for many plants and crops worldwide and produce valuable hive products such as honey and wax. Various sources of stress can disrupt honey bee colonies, affecting their health and productivity. Growing evidence suggests that honey is vitally important to hive functioning and overall health. In this study, we determined the antimicrobial activity and chemical properties of honey from healthy hives and hives showing signs of stress, finding that honey from healthy hives was significantly more antimicrobial, with increased phenolics and antioxidant content. We next profiled the bacterial and fungal microbiome of the bee gut and the hive environment, finding significant differences between healthy and stressed hives. Our results underscore the need for greater understanding in this area, as we found even apparently minor stress can have implications for overall hive fitness as well as the economic potential of hive products.

The effects of glyphosate, pure or in herbicide formulation, on bumble bees and their gut microbial communities

The widespread use of glyphosate-based formulations to eliminate unwanted vegetation has increased concerns regarding their effects on non-target organisms, such as honey bees and their gut microbial communities. These effects have been associated with both glyphosate and co-formulants, but it is still unknown whether they translate to other bee species. In this study, we tested whether glyphosate, pure or in herbicide formulation, can affect the gut microbiota and survival rates of the eastern bumble bee, Bombus impatiens. We performed mark-recapture experiments with bumble bee workers from four different commercial colonies, which were exposed to field relevant concentrations of glyphosate or a glyphosate-based formulation (0.01 mM to 1 mM). After a 5-day period of exposure, we returned the bees to their original colonies, and they were sampled at days 0, 3 and 7 post-exposure to investigate changes in microbial community and microbiota resilience by 16S rRNA amplicon sequencing and quantitative PCR. We found that exposure to glyphosate, pure or in herbicide formulation, reduced the relative abundance of a beneficial bee gut bacterium, Snodgrassella, in bees from two of four colonies when compared to control bees at day 0 post-exposure, but this reduction became non-significant at days 3 and 7 post-exposure, suggesting microbiota resilience. We did not find significant changes in total bacteria between control and exposed bees. Moreover, we observed an overall trend in decreased survival rates in bumble bees exposed to 1 mM herbicide formulation during the 7-day post-exposure period, suggesting a potential negative effect of this formulation on bumble bees.

Effect of Chronic Exposure to Sublethal Doses of Imidacloprid and Nosema ceranae on Immunity, Gut Microbiota, and Survival of Africanized Honey Bees

Large-scale honey bee colony losses reported around the world have been associated with intoxication with pesticides, as with the presence of pests and pathogens. Among pesticides, neonicotinoid insecticides are the biggest threat. Due to their extensive use, they can be found in all agricultural environments, including soil, water, and air, are persistent in the environment, and are highly toxic for honey bees. In addition, infection by different pests and pathogens can act synergistically, weakening bees. In this study, we investigated the effects of chronic exposure to sublethal doses of imidacloprid alone or combined with the microsporidia Nosema ceranae on the immune response, deformed wing virus infection (DWV), gut microbiota, and survival of Africanized honey bees. We found that imidacloprid affected the expression of some genes associated with immunity generating an altered physiological state, although it did not favor DWV or N. ceranae infection. The pesticide alone did not affect honey bee gut microbiota, as previously suggested, but when administered to N. ceranae infected bees, it generated significant changes. Finally, both stress factors caused high mortality rates. Those results illustrate the negative impact of imidacloprid alone or combined with N. ceranae on Africanized honey bees and are useful to understand colony losses in Latin America.

Evaluating the Impact of Commonly Used Pesticides on Honeybees (Apis mellifera) in North Gonder of Amhara Region, Ethiopia

Global honeybee losses and colony decline are becoming continuous threat to the apicultural industry, as well as, for food security and environmental stability. Although the putative causes are still unclear, extensive exposure of bees to pesticides could be the possible factor for worldwide colony losses. This study was aimed at evaluating the impact of nine commonly used pesticide incidents on adult worker honeybees (A. mellifera) under the laboratory condition, in North Gonder of Amhara region, Ethiopia. Feeding test, contact test, and fumigation tests were carried out for each pesticide following the standard procedures, and each pesticide toxicity was compared to the standard toxic chemical, dimethoate 40% EC (positive control), and to 50% honey solution (negative control). The results revealed that all the tested pesticides caused significant deaths of the experimental bees ( $P<0.05$ ) in all the tests when compared to the negative control. Diazinon 60% EC, endosulfan 35% EC, and malathion 50% EC were appeared highly toxic causing 100% mortality of bees, while chlorsulfuron 75% WG killed 90% of the experimental bees as tested via feeding. On the other hand, agro-2, 4-D and its mixture with glycel 41% EC are moderately toxic, and mancozeb 80% WP and glycel 41% EC were slightly toxic to honeybees as compared to the positive control (dimethoate 40% EC). Suddenly, diazinon 60% EC and malathion 50% EC triggered 100% mortality of bees, while endosulfan 35% EC and chlorsulfuron 75% WG caused 63.63% and 90.82% of bee mortality, respectively, when evaluated via contact test. The fumigation test also showed that chlorsulfuron 75% WG, diazinon 60% EC, and endosulfan 35% EC caused 100%, 86.7%, and 65.6% mortality rate of bees. Our result also highlighted that tested LD50 of all pesticide incidents were significantly lower than the manufacturer-based LD50. This shows that local honeybees A. m. jemenetica are extremely sensitive to commonly used agricultural pesticides, which may affect the colony level due to the intensive application of these pesticides in Ethiopia.

Toxic effects of glyphosate on histopathology and intestinal microflora of juvenile Litopenaeus vannamei

Glyphosate is a widely used broad-spectrum herbicide, its pollution to the surrounding conditions can't be ignored. It has been reported that glyphosate has poisonous impacts on aquatic animals. In this study, juvenile Litopenaeus vannamei (L. vannamei) was exposed to glyphosate, and the lethal concentration 50 (LC₅₀) of glyphosate to juvenile L. vannamei for 48 h was 47.6 mg/L. The histological analysis for intestine and hepatopancreas and the intestinal microorganisms of L. vannamei were evaluated after 48 h of exposure to glyphosate with LC₅₀. The histological analysis results showed that the lumen of hepatic tubules was diffused and deformed, the hepatic tubules were ruptured and intestinal villi were fallen off seriously after exposure to glyphosate for 48 h Moreover, the intestinal microbial composition and structure of L. vannamei were changed, with the abundance of Alphaproteobacteria increased significantly. The abundance of Rhodobacteraceae, Vibrio and Legionella increased, but there was no significant difference. The abundance of Bacillus, Paraburkholderia, Enhydrobacter, Comamonas and Alkanindiges decreased significantly. However, the homeostasis of intestinal microorganisms was destroyed. Phenotypic prediction of the two groups of microorganisms revealed a significant increase in the abundance of Facultatively Anaerobic in the glyphosate challenged group. This study suggested that hepatopancreas and intestinal tissue of L. vannamei were seriously damaged after 48 h of exposure to glyphosate with LC₅₀, and intestinal microbial homeostasis was disrupted.

Strategies and techniques to mitigate the negative impacts of pesticide exposure to honey bees

In order to support food, fiber, and fuel production around the world, billions of kilograms of pesticides are applied to crop fields every year to suppress pests, plant diseases and weeds. These fields are often home to the most important commercial pollinators, honey bees (Apis spp.), which improve yield and quality of many agricultural products. The pesticides applied to support crop health can be detrimental to honey bee health. The conflict of pesticide use and reliance on honey bees contributes to significant honey bee colony losses across the world. Recommendations for reducing impact on honey bees are generally suggested in literature, pesticide regulations, and by crop consultants, but without a considerable discussion of the realistic limitations of protecting honey bees. New techniques in farming and beekeeping can reduce pesticide exposure through reduction in bee exposure, reduced toxicity of pesticides, and remedies that can be in response to exposure. However, lack of assessment of those new techniques under a systematical, comprehensive framework may overestimate or underestimate these techniques' potential to protect honey bees from pesticide damage. In this review, we summarize the current and arising strategies and techniques with the goal to inspire the development and adoption of pesticide mitigation practices for both agriculture and apiculture.

Field-realistic acute exposure to glyphosate-based herbicide impairs fine-color discrimination in bumblebees

Pollinator decline is a grave challenge worldwide. One of the main culprits for this decline is the widespread use of, and pollinators' chronic exposure to, agrochemicals. Here, we examined the effect of a field-realistic dose of the world's most commonly used pesticide, glyphosate-based herbicide (GBH), on bumblebee cognition. We experimentally tested bumblebee (Bombus terrestris) color and scent discrimination using acute GBH exposure, approximating a field-realistic dose from a day's foraging in a patch recently sprayed with GBH. In a 10-color discrimination experiment with five learning bouts, GBH treated bumblebees' learning rate fell to zero by third learning bout, whereas the control bees increased their performance in the last two bouts. In the memory test, the GBH treated bumblebees performed to near chance level, indicating that they had lost everything they had learned during the learning bouts, while the control bees were performing close to the level in their last learning bout. However, GBH did not affect bees' learning in a 2-color or 10-odor discrimination experiment, which suggests that the impact is limited to fine color learning and does not necessarily generalize to less specific tasks or other modalities. These results indicate that the widely used pesticide damages bumblebees' fine-color discrimination, which is essential to the pollinator's individual success and to colony fitness in complex foraging environments. Hence, our study suggests that acute sublethal exposure to GBH poses a greater threat to pollination-based ecosystem services than previously thought, and that tests for learning and memory should be integrated into pesticide risk assessment.

Azoxystrobin Disrupts Colonic Barrier Function in Mice via Metabolic Disorders Mediated by Gut Microbiota

The widespread use of azoxystrobin (AZO) over the past few decades has drawn great attention to its environmental health effects. The objective of the present study was to explore the effects of AZO on intestinal barrier function in mice from the perspective of gut microbiota. Specifically, exposure to AZO could cause colonic barrier dysfunction in mice. Meanwhile, AZO could also cause dysbiosis of gut microbiota. Further studies revealed that the metabolic profile of the microbiota was significantly disturbed with AZO exposure. Last but not least, we confirmed that the gut microbiota played a central role in AZO-induced colonic barrier dysfunction through the gut microbiota transplantation experiment. Gut microbiota mediated colonic barrier dysfunction induced by AZO via inducing dysbiosis of the microbiota metabolic profile. The findings of this study strongly support a new insight that the gut microbiota can be a key target of health risks of pesticides.

Effects of spinetoram and glyphosate on physiological biomarkers and gut microbes in Bombus terrestris

The sublethal effects of pesticide poisoning will have significant negative impacts on the foraging and learning of bees and bumblebees, so it has received widespread attention. However, little is known about the physiological effects of sublethal spinetoram and glyphosate exposure on bumblebees. We continuously exposed Bombus terrestris to sublethal (2.5 mg/L) spinetoram or glyphosate under controlled conditions for 10 days. The superoxide dismutase, glutathione-S-transferase, carboxylesterase, prophenoloxidase, α-amylase and protease activities, and changes in gut microbes were measured to understand the effects of sublethal pesticide exposure on the physiology and gut microbes of bumblebees. Sublethal pesticide exposure to significantly increased superoxide dismutase activity and significantly decreased gut α-amylase activity in bumblebees but had no significant effect on glutathione-S-transferase, carboxylesterase or gut protease activities. In addition, glyphosate increased the activity of prophenoloxidase. Interestingly, we observed that neither of the two pesticides had a significant effect on dominant gut bacteria, but glyphosate significantly altered the structure of the dominant gut fungal community, and reduced the relative abundance of Zygosaccharomyces associated with fat accumulation. These results suggest that sublethal spinetoram and glyphosate do not significantly affect the detoxification system of bumblebees, but may affect bumblebee health by inhibiting energy acquisition. Our results provide information on the sublethal effects of exposure to low concentrations of glyphosate and spinetoram on bumblebees in terms of physiology and gut microbes.

Developing Strategies to Help Bee Colony Resilience in Changing Environments

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.

Binding and Detoxification of Insecticides by Potentially Probiotic Lactic Acid Bacteria Isolated from Honeybee (Apis mellifera L.) Environment-An In Vitro Study

Lactic acid bacteria (LAB) naturally inhabiting the digestive tract of honeybees are known for their ability to detoxify xenobiotics. The effect of chlorpyrifos, coumaphos, and imidacloprid on the growth of LAB strains was tested. All strains showed high resistance to these insecticides. Subsequently, the insecticide binding ability of LAB was investigated. Coumaphos and chlorpyrifos were bound to the greatest extent (up to approx. 64%), and imidacloprid to a much weaker extent (up to approx. 36%). The insecticides were detected in extra- and intracellular extracts of the bacterial cell wall. The ability of selected LAB to reduce the cyto- and genotoxicity of insecticides was tested on two normal (ovarian insect Sf-9 and rat intestinal IEC-6) cell lines and one cancer (human intestinal Caco-2) cell line. All strains exhibited various levels of reduction in the cyto- and genotoxicity of tested insecticides. It seems that coumaphos was detoxified most potently. The detoxification abilities depended on the insecticide, LAB strain, and cell line. The detoxification of insecticides in the organisms of honeybees may reduce the likelihood of the penetration of these toxins into honeybee products consumed by humans and may contribute to the improvement of the condition in apiaries and honeybee health.

The gut microbiota affects the social network of honeybees

The gut microbiota influences animal neurodevelopment and behaviour but has not previously been documented to affect group-level properties of social organisms. Here, we use honeybees to probe the effect of the gut microbiota on host social behaviour. We found that the microbiota increased the rate and specialization of head-to-head interactions between bees. Microbiota colonization was associated with higher abundances of one-third of the metabolites detected in the brain, including amino acids with roles in synaptic transmission and brain energetic function. Some of these metabolites were significant predictors of the number of social interactions. Microbiota colonization also affected brain transcriptional processes related to amino acid metabolism and epigenetic modifications in a brain region involved in sensory perception. These results demonstrate that the gut microbiota modulates the emergent colony social network of honeybees and suggest changes in chromatin accessibility and amino acid biosynthesis as underlying processes.

Chronic Effects of Dietary Pesticides on the Gut Microbiome and Neurodevelopment

Many agricultural pesticides include substances that are known to be harmful to human health and while some have been banned from developed countries, they are still being used in developing countries such as Brazil. Recent studies have shown that low-level chronic dietary exposure to pesticides can affect the human gut microbiota. This possible hazardous effect of pesticides on human health has not been specifically recognized by government regulatory agencies. In Brazil, for instance, of the 10 best-selling active ingredients in pesticides in 2019, two are considered extremely toxic, Paraquat and Chlorpyrifos. Even though Paraquat has been banned in Brazil since 2020, the values of maximum residue limits (MRLs) of toxic pesticides allowed in the country are still higher than in other countries. Unfortunately, many developing countries still lack the resources and expertise needed to monitor adequately and systematically the presence of pesticide residues on food. In this work, we raise awareness to the danger the chronic exposure to high dietary levels of pesticides can pose to the public, especially considering their prolonged effects on the gut microbiome.