Are commercial probiotics and prebiotics effective in the treatment and prevention of honeybee nosemosis C?

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.

Probiotic Potential of Bacillus Subtilis Strain I3: Antagonistic Activity Against Chalkbrood Pathogen and Pesticide Degradation for Enhancing Honeybee Health

To explore the potential of probiotic candidates beneficial for honeybee health through the modulation of the gut microbiome, bee gut microbes were isolated from bumblebee (Bombus terrestris) and honeybee (Apis mellifera) using diverse media and cultural conditions. A total of 77 bee gut bacteria, classified under the phyla Proteobacteria, Firmicutes, and Actinobacteria, were identified. The antagonistic activity of the isolates against Ascosphaera apis, a fungal pathogen responsible for chalkbrood disease in honeybee larvae, was investigated. The highest growth inhibition percentage against A. apis was demonstrated by Bacillus subtilis strain I3 among the bacterial strains. The presence of antimicrobial peptide genes in the I3 strain was detected using PCR amplification of gene fragments encoding surfactin and fengycin utilizing specific primers. The export of antimicrobial peptides by the I3 strain into growth medium was verified using liquid chromatography coupled with mass spectroscopy. Furthermore, the strain's capabilities for degrading pesticides, used for controlling varroa mites, and its spent growth medium antioxidant activity were substantiated. The survival rate of honeybees infected with (A) apis was investigated after feeding larvae with only medium (fructose + glucose + yeast extract + royal jelly), (B) subtilis I3 strain, A. apis with medium and I3 strain + A. apis with medium. Honeybees receiving the I3 strain + A. apis exhibited a 50% reduction in mortality rate due to I3 strain supplementation under experimental conditions, compared to the control group. In silico molecular docking revealed that fengycin hydrolase from I3 strain effectively interacted with tau-fluvalinate, suggesting its potential in bee health and environmental protection. Further studies are needed to confirm the effects of the I3 strain in different populations of honey bees across several regions to account for genetic and environmental variations.

Interactions between microsporidia and other members of the microbiome

The microbiome is the collection of microbes that are associated with a host. Microsporidia are intracellular eukaryotic parasites that can infect most types of animals. In the last decade, there has been much progress to define the relationship between microsporidia and the microbiome. In this review, we cover an increasing number of reports suggesting that microsporidia are common components of the microbiome in both invertebrates and vertebrates. These microsporidia infections can range from mutualistic to pathogenic, causing several physiological phenotypes, including death. Infection with microsporidia often causes a disruption in the normal microbiome, with both increases and decreases of bacterial, fungal, viral, and protozoan species being observed. This impact on the microbiome can occur through upregulation and downregulation of innate immunity as well as morphological changes to tissues that impact interactions with these microbes. Other microbes, particularly bacteria, can inhibit microsporidia and have been exploited to control microsporidia infections. These bacteria can function through regulating immunity, secreting anti-microsporidia compounds, and, in engineered versions, expressing double-stranded RNA targeting microsporidia genes. We end this review by discussing potential future directions to further understand the complex interactions between microsporidia and the other members of the microbiome.

Probiotics and in-hive fermentation as a source of beneficial microbes to support the gut microbial health of honey bees

Managed populations of honey bees (Apis mellifera Linnaeus; Hymenoptera: Apidae) are regularly exposed to infectious diseases. Good hive management including the occasional application of antibiotics can help mitigate infectious outbreaks, but new beekeeping tools and techniques that bolster immunity and help control disease transmission are welcome. In this review, we focus on the applications of beneficial microbes for disease management as well as to support hive health and sustainability within the apicultural industry. We draw attention to the latest advances in probiotic approaches as well as the integration of fermented foods (such as water kefir) with disease-fighting properties that might ultimately be delivered to hives as an alternative or partial antidote to antibiotics. There is substantial evidence from in vitro laboratory studies that suggest beneficial microbes could be an effective method for improving disease resistance in honey bees. However, colony level evidence is lacking and there is urgent need for further validation via controlled field trials experimentally designed to test defined microbial compositions against specific diseases of interest.

Delivery mechanism can enhance probiotic activity against honey bee pathogens

Managed honey bee (Apis mellifera) populations play a crucial role in supporting pollination of food crops but are facing unsustainable colony losses, largely due to rampant disease spread within agricultural environments. While mounting evidence suggests that select lactobacilli strains (some being natural symbionts of honey bees) can protect against multiple infections, there has been limited validation at the field-level and few methods exist for applying viable microorganisms to the hive. Here, we compare how two different delivery systems-standard pollen patty infusion and a novel spray-based formulation-affect supplementation of a three-strain lactobacilli consortium (LX3). Hives in a pathogen-dense region of California are supplemented for 4 weeks and then monitored over a 20-week period for health outcomes. Results show both delivery methods facilitate viable uptake of LX3 in adult bees, although the strains do not colonize long-term. Despite this, LX3 treatments induce transcriptional immune responses leading to sustained decreases in many opportunistic bacterial and fungal pathogens, as well as selective enrichment of core symbionts including Bombilactobacillus, Bifidobacterium, Lactobacillus, and Bartonella spp. These changes are ultimately associated with greater brood production and colony growth relative to vehicle controls, and with no apparent trade-offs in ectoparasitic Varroa mite burdens. Furthermore, spray-LX3 exerts potent activities against Ascosphaera apis (a deadly brood pathogen) likely stemming from in-hive dispersal differences, whereas patty-LX3 promotes synergistic brood development via unique nutritional benefits. These findings provide a foundational basis for spray-based probiotic application in apiculture and collectively highlight the importance of considering delivery method in disease management strategies.

Beneficial bacteria as biocontrol agents for American foulbrood disease in honey bees (Apis mellifera)

American foulbrood (AFB) is a cosmopolitan bacterial disease that affects honey bee (Apis mellifera) larvae and causes great economic losses in apiculture. Currently, no satisfactory methods are available for AFB treatment mainly due to the difficulties to eradicate the tenacious spores produced by the etiological agent of AFB, Paenibacillus larvae (Bacillales, Paenibacillaceae). This present review focused on the beneficial bacteria that displayed antagonistic activities against P. larvae and demonstrated potential in AFB control. Emphases were placed on commensal bacteria (genus Bacillus and lactic acid bacteria in particular) in the alimentary tract of honey bees. The probiotic roles lactic acid bacteria play in combating the pathogenic P. larvae and the limitations referring to the application of these beneficial bacteria were addressed.

Disentangling the microbial ecological factors impacting honey bee susceptibility to Paenibacillus larvae infection

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.

Natural Substances, Probiotics, and Synthetic Agents in the Treatment and Prevention of Honeybee Nosemosis

Honeybees are important pollinators, but they are continuously exposed to a variety of fungal and bacterial diseases. One of the various diseases affecting honeybees is nosemosis caused by microsporidia from the Nosema genus. Honeybees are mainly infected through consumption of infected food or faeces containing Nosema spp. spores. Nosemosis causes damage to the middle intestine epithelium, which leads to food absorption disorders and honeybee malnutrition. Fumagillin, i.e., the antibiotic used to treat nosemosis, was withdrawn in 2016 from EU countries. Therefore, researchers have been looking for compounds of both natural and synthetic origin to fight nosemosis. Such compounds should not have a negative impact on bees but is expected to inhibit the disease. Natural compounds tested against nosemosis include, e.g., essential oils (EOs), plant extracts, propolis, and bacterial metabolites, while synthetic substances tested as anti-nosemosis agents are represented by porphyrins, vitamins, antibiotics, phenolic, ascorbic acids, and others. This publication presents an 18-year overview of various studies of a number of natural and synthetic compounds used in the treatment and prevention of nosemosis cited in PubMed, GoogleScholar, and CrossRef.

Effect of amide protoporphyrin derivatives on immune response in Apis mellifera

The intracellular microsporidian parasite Nosema ceranae is known to compromise bee health by induction of energetic stress and downregulation of the immune system. Porphyrins are candidate therapeutic agents for controlling Nosema infection without adverse effects on honeybees. In the present work, the impact of two protoporphyrin IX derivatives, i.e. PP[Asp]₂ and PP[Lys]₂, on Apis mellifera humoral immune response has been investigated in laboratory conditions in non-infected and N. ceranae-infected honeybees. Fluorescence spectroscopy analysis of hemolymph showed for the first time that porphyrin molecules penetrate into the hemocoel of honeybees. Phenoloxidase (PO) activity and the expression of genes encoding antimicrobial peptides (AMPs: abaecin, defensin, and hymenoptaecin) were assessed. Porphyrins significantly increased the phenoloxidase activity in healthy honeybees but did not increase the expression of AMP genes. Compared with the control bees, the hemolymph of non-infected bees treated with porphyrins had an 11.3- and 6.1-fold higher level of PO activity after the 24- and 48-h porphyrin administration, respectively. Notably, there was a significant inverse correlation between the PO activity and the AMP gene expression level (r =  - 0.61696, p = 0.0143). The PO activity profile in the infected bees was completely opposite to that in the healthy bees (r =  - 0.5118, p = 0.000), which was related to the changing load of N. ceranae spores in the porphyrin treated-bees. On day 12 post-infection, the spore loads in the infected porphyrin-fed individuals significantly decreased by 74%, compared with the control bees. Our findings show involvement of the honeybee immune system in the porphyrin-based control of Nosema infection. This allows the infected bees to improve their lifespan considerably by choosing an optimal PO activity/AMP expression variant to cope with the varying level of N. ceranae infection.

Bumblebees with the socially transmitted microbiome: A novel model organism for gut microbiota research

Eusocial bumble and honey bees are important pollinators for global ecology and the agricultural economy. Although both the bumble and honey bees possess similar and host-restricted gut microbiota, they differ in aspects of morphology, autonomy, physiology, behavior, and life cycle. The social bee gut bacteria exhibit host specificity that is likely a result of long-term co-evolution. The unique life cycle of bumblebees is key for the acquisition and development of their gut microbiota, and affects the strain-level diversity of the core bacterial species. Studies on bumblebee gut bacteria show that they retain less functional capacity for carbohydrate metabolism compared with that of the honeybee. We discuss the potential roles of the bumblebee gut microbiota against pathogenic threats and the application of host-specific probiotics for bumblebees. Given the advantages of the bumblebee microbiome, including the simple structure and host specificity, and the ease of manipulating bumblebee colonies, we propose that bumblebees may provide a valuable system for understanding the general principles of host-microbe interactions, gut-brain axis, and vertical transmission.

Antifungal activity of "HO21-F", a formulation based on Olea europaea plant extract, in honey bees infected with Nosema ceranae

Nosema ceranae is a microsporidium parasite that silently affects honey bees, causing a disease called nosemosis. This parasite produces resistant spores and germinates in the midgut of honey bees, extrudes a polar tubule that injects an infective sporoplasm in the host cell epithelium, proliferates, and produces intestinal disorders that shorten honey bee lifespan. The rapid extension of this disease has been reported to be widespread among adult bees, and treatments are less effective and counterproductive weakening colonies. This work aimed to evaluate the antifungal activity of a prototype formulation based on a non-toxic plant extract (HO21-F) against N. ceranae. In laboratory, honey bees were infected artificially, kept in cages for 17 days and samples were taken at 7 and 14 days post infection (dpi). At the same time, in field conditions we evaluated the therapeutic effect of HO21-F for 28 days in naturally infected colonies. The effectiveness of the treatment has been demonstrated by a reduction of 83.6 % of the infection levels observed in laboratory conditions at concentrations of 0.5 and 1 g/L without affecting the survival rate. Besides, in-field conditions we reported a reduction of 88 % of the infection level at a concentration of 2.5 g/L, obtaining better antifungal effectiveness in comparison to other commercially available treatments. As a result, we observed that the use of HO21-F led to an increase in population size and honey production, both parameters associated with colony strength. The reported antifungal activity of HO21-F against N. ceranae, with a significant control of spore proliferation in worker bees, suggests the promising commercial application use of this product against nosemosis, and it will encourage new research studies to understand the mechanism of action, whether related to the spore-inhibition effect and/or a stimulating effect in natural response of colonies to counteract the disease.

Prospects for probiotics in social bees

Social corbiculate bees are major pollinators. They have characteristic bacterial microbiomes associated with their hives and their guts. In honeybees and bumblebees, worker guts contain a microbiome composed of distinctive bacterial taxa shown to benefit hosts. These benefits include stimulating immune and metabolic pathways, digesting or detoxifying food, and defending against pathogens and parasites. Stressors including toxins and poor nutrition disrupt the microbiome and increase susceptibility to opportunistic pathogens. Administering probiotic bacterial strains may improve the health of individual bees and of hives, and several commercial probiotics are available for bees. However, evidence for probiotic benefits is lacking or mixed. Most bacterial species used in commercial probiotics are not native to bee guts. We present new experimental results showing that cultured strains of native bee gut bacteria colonize robustly while bacteria in a commercial probiotic do not establish in bee guts. A defined community of native bee gut bacteria resembles unperturbed native gut communities in its activation of genes for immunity and metabolism in worker bees. Although many questions remain unanswered, the development of natural probiotics for honeybees, or for commercially managed bumblebees, is a promising direction for protecting the health of managed bee colonies.

This article is part of the theme issue ‘Natural processes influencing pollinator health: from chemistry to landscapes’.

Comparison of the gut microbiome of sacbrood virus-resistant and -susceptible Apis cerana from South Korea

Honey bees are important pollinators for the conservation of the ecosystem and agricultural products and provide a variety of products important for human use, such as honey, pollen, and royal jelly. Sacbrood disease (SD) is a devastating viral disease in Apis cerana; an effective preventive measure for SD is urgently needed. In this study, the relationship between the gut microbiome of honey bees and SD was investigated by pyrosequencing. Results revealed that sacbrood virus (SBV)-resistant A. cerana strains harbour a unique acetic acid bacterium, Bombella intestini, and the lactic acid bacteria (LAB) Lactobacillus (unclassified)_uc, Bifidobacterium longum, B. catenulatum, Lactococcus lactis, and Leuconostoc mesenteroides in larvae and Hafnia alvei, B. indicum, and the LAB L. mellifer and Lactobacillus HM215046_s in adult bees. Changes in the gut microbiome due to SBV infection resulted in loss of bacteria that could affect host nutrients and inhibit honey bee pathogens, such as Gilliamella JFON_s, Gilliamella_uc, Pseudomonas putida, and L. kunkeei in A. cerana larvae and Frischella_uc, Pantoea agglomerans, Snodgrassella_uc, and B. asteroides in adult bees. These findings provide important information for the selection of probiotics for A. cerana larvae and adults to prevent pathogenic infections and keep honey bees healthy.

Antimicrobial Activity from Putative Probiotic Lactic Acid Bacteria for the Biological Control of American and European Foulbrood Diseases

The balance of the gut microbiome is important for the honey bee’s growth and development, immune function and defense against pathogens. The use of a beneficial bacteria-based strategy for the prevention and biocontrol of American foulbrood (AFB) and European foulbrood (EFB) diseases in honey bees offers interesting prospects. Lactic acid bacteria (LAB) are common inhabitants of the gastrointestinal tract of the honey bee. Among LABs associated with bee gut microbiota, Lactiplantibacillus plantarum (previously Lactobacillus plantarum) and Apilactobacillus kunkeei (formerly classified as Lactobacillus kunkeei) are two of the most abundant species. In this study, four Lactiplantibacillus plantarum strains and four Apilactobacillus kunkeei strains, isolated from the gastrointestinal tract of honey bee (Apis mellifera L.) were selected for their in vitro inhibition ability of Paenibacillus larvae ATCC 9545 and Melissococccus plutonius ATCC 35311. In addition, these LABs have been characterized through some biochemical and functional characteristics: cell surface properties (hydrophobicity and auto-aggregation), carbohydrates assimilation and enzymatic activities. The antimicrobial, biochemical and cell surface properties of these LABs have been functional to their candidature as potential probiotics in beekeeping and for the biocontrol of AFB and EFB diseases.

Activities of Antioxidant and Proteolytic Systems and Biomarkers in the Fat Body and Hemolymph of Young Apis mellifera Females

Simple Summary

The proteolytic system consists of compounds that, similar to “scissors”, cut proteins found in bee cells (e.g., to activate these proteins) or released by pathogens. During these reactions, reactive oxygen species are created and then removed by antioxidants. The actions of the proteolytic and antioxidant systems are enhanced by biomarkers. These compounds are produced mainly in the fat body and then released into the hemolymph. We determined the activities of these compounds in various localizations/segments of the fat body and in the hemolymph in females with increased reproductive potential, i.e., queens and rebels, and in normal (sterile non-rebel) workers. Rebels are workers who resemble the queen in terms of anatomical, behavioural, and physiological features. It was revealed that the activities of these compounds in the rebels were between those of queens and normal workers. Normal workers had higher activities of the proteolytic and antioxidant systems in the fat body and hemolymph than the other females. These results are important for understanding the functioning of the fat body, the stress ecology, and the formation of the different castes of Apis mellifera females.

Abstract

The proteolytic and antioxidant systems are important components of humoral immunity, and these biomarkers indicate the immune status. These compounds are synthesized in the bees’ fat body and released into the hemolymph. Their functions maintain the organism’s homeostasis and protect it against adverse environmental factors (including pathogens). We determined the activities of acidic, neutral, and alkaline proteases and their inhibitors, as well as superoxide dismutase (SOD), catalase (CAT), aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), and the level of total antioxidant potential (TAC). These compounds were investigated in the fat body and hemolymph in the females with increased reproductive potential, i.e., queens and rebels, and in normal (non-reproductive sterile non-rebel) workers. The phenoloxidase (PO) activities were determined in the hemolymph. The normal workers had higher activities of proteases and their inhibitors, SOD and CAT, in the fat body and hemolymph, compared to the queens and rebels. The protease inhibitors were not usually active in the queens. As we predicted, the rebels revealed values between those of the queens and normal workers. The highest activities of proteases and antioxidants were identified in the fat body from the third tergite in comparison with the sternite and the fifth tergite. These results are important for oxidative stress ecology and give a better understanding of the functioning of the fat body and the division of labor in social insects.

Bee Stressors from an Immunological Perspective and Strategies to Improve Bee Health

Honeybees are the most prevalent insect pollinator species; they pollinate a wide range of crops. Colony collapse disorder (CCD), which is caused by a variety of biotic and abiotic factors, incurs high economic/ecological loss. Despite extensive research to identify and study the various ecological stressors such as microbial infections, exposure to pesticides, loss of habitat, and improper beekeeping practices that are claimed to cause these declines, the deep understanding of the observed losses of these important insects is still missing. Honeybees have an innate immune system, which includes physical barriers and cellular and humeral responses to defend against pathogens and parasites. Exposure to various stressors may affect this system and the health of individual bees and colonies. This review summarizes and discusses the composition of the honeybee immune system and the consequences of exposure to stressors, individually or in combinations, on honeybee immune competence. In addition, we discuss the relationship between bee nutrition and immunity. Nutrition and phytochemicals were highlighted as the factors with a high impact on honeybee immunity.

Recent Advances in the Biocontrol of Nosemosis in Honey Bees (Apis mellifera L.)

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.

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

Simple Summary

Honey bees play a pivotal role in the sustainability of ecosystems and biodiversity. Many factors including parasites, pathogens, pesticide residues, forage losses, and poor nutrition have been proposed to explain honey bee colony losses. Lactic acid bacteria (LAB) are normal inhabitants of the gastrointestinal tract of honey bees and their role has been consistently reported in the literature. In recent years, there have been numerous scientific evidence that the intestinal microbiota plays an essential role in honey bee health. Management strategies, based on supplementation of the gut microbiota with probiotics, may be important to increase stress tolerance and disease resistance. In this review, recent scientific advances on the use of LABs as microbial supplements in the diet of honey bees are summarized and discussed.

Abstract

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.

Current Therapy and Therapeutic Targets for Microsporidiosis

Microsporidia are obligate intracellular, spore-forming parasitic fungi which are grouped with the Cryptomycota. They are both opportunistic pathogens in humans and emerging veterinary pathogens. In humans, they cause chronic diarrhea in immune-compromised patients and infection is associated with increased mortality. Besides their role in pébrine in sericulture, which was described in 1865, the prevalence and severity of microsporidiosis in beekeeping and aquaculture has increased markedly in recent decades. Therapy for these pathogens in medicine, veterinary, and agriculture has become a recent focus of attention. Currently, there are only a few commercially available antimicrosporidial drugs. New therapeutic agents are needed for these infections and this is an active area of investigation. In this article we provide a comprehensive summary of the current as well as several promising new agents for the treatment of microsporidiosis including: albendazole, fumagillin, nikkomycin, orlistat, synthetic polyamines, and quinolones. Therapeutic targets which could be utilized for the design of new drugs are also discussed including: tubulin, type 2 methionine aminopeptidase, polyamines, chitin synthases, topoisomerase IV, triosephosphate isomerase, and lipase. We also summarize reports on the utility of complementary and alternative medicine strategies including herbal extracts, propolis, and probiotics. This review should help facilitate drug development for combating microsporidiosis.

Study of the dual biological impacts of aqueous extracts of normal and gamma-irradiated Galleria mellonella larvae

Objectives

Galleria mellonella assimilates beeswax using many gut enzymes; however, high doses of gamma radiation have been used to eradicate such pests, affecting its life cycle. In vitro studies of irradiated extracts of G. mellonella against bacterial species as well as three tumour cell lines are demonstrated in the present study. The antibacterial and antitumour effects are compared with those of the non-irradiated Galleria mellonella larval extract.

Methods

The effect of different dose levels of gamma irradiation, ranging from 2 to 8 Gy, was tested on G. mellonella lipase, protease, and acid phosphate activities. The antimicrobial activity of un-irradiated and irradiated G. mellonella larval extracts was tested against different gram-positive and gram-negative bacteria and some fungi. The antitumour action was tested against different tumour cell lines. A cytotoxicity assay was performed on normal and irradiated larval extracts against normal human lung fibroblast cells. A microscopic examination of Streptococcus mutants and HepG-2 was performed using transmission and scanning electron microscopy.

Results

Optimum results were obtained at 6 Gy, which enhanced maximum enzymatic activity. Maximum antimicrobial activity was obtained against Streptococcus mutants with MIC 31.25 μg/ml at a dose of 6 Gy. A microscopic examination depicted an apoptotic process for irradiated G. mellonella larvae with either Streptococcus mutants or HepG-2.

Conclusion

The present study shows a synergistic relationship between the G. mellonella larval extract and a 6 Gy radiation dose for further biomedical applications.

Field-Realistic Tylosin Exposure Impacts Honey Bee Microbiota and Pathogen Susceptibility, Which Is Ameliorated by Native Gut Probiotics

Antibiotics have been applied to honey bee (Apis mellifera) hives for decades to treat Paenibacillus larvae, which causes American foulbrood disease and kills honey bee larvae. One of the few antibiotics approved in apiculture is tylosin tartrate. This study examined how a realistic hive treatment regimen of tylosin affected the gut microbiota of bees and susceptibility to a bacterial pathogen. Tylosin treatment reduced bacterial species richness and phylogenetic diversity and reduced the absolute abundances and strain diversity of the beneficial core gut bacteria Snodgrassella alvi and Bifidobacterium spp. Bees from hives treated with tylosin died more quickly after being fed a bacterial pathogen (Serratia marcescens) in the laboratory. We then tested whether a probiotic cocktail of core bee gut species could bolster pathogen resistance. Probiotic exposure increased survival of bees from both control and tylosin-treated hives. Finally, we measured tylosin tolerance of core bee gut bacteria by plating cultured isolates on media with different tylosin concentrations. We observed highly variable responses, including large differences among strains of both S. alvi and Gilliamella spp. Thus, probiotic treatments using cultured bee gut bacteria may ameliorate harmful perturbations of the gut microbiota caused by antibiotics or other factors. IMPORTANCE The antibiotic tylosin tartrate is used to treat honey bee hives to control Paenibacillus larvae, the bacterium that causes American foulbrood. We found that bees from tylosin-treated hives had gut microbiomes with depleted overall diversity as well as reduced absolute abundances and strain diversity of the beneficial bee gut bacteria Snodgrassella alvi and Bifidobacterium spp. Furthermore, bees from treated hives suffered higher mortality when challenged with an opportunistic pathogen. Bees receiving a probiotic treatment, consisting of a cocktail of cultured isolates of native bee gut bacteria, had increased survival following pathogen challenge. Thus, probiotic treatment with native gut bacteria may ameliorate negative effects of antibiotic exposure.

Lactobacillus salivarius A3iob Reduces the Incidence of Varroa destructor and Nosema Spp. in Commercial Apiaries Located in the Northwest of Argentina

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.

Insight into probiotic properties of lactic acid bacterial endosymbionts of Apis mellifera L. derived from the Polish apiary

Taking into account that fructophilic lactic acid bacteria (FLAB) can play an important role in the health of honey bees and can be used as probiotics, phenotypic properties of probiotic interest of Lactobacillus kunkeei (12 strains) and Fructobacillus fructossus bacteria (2 strains), isolated from Apis mellifera gastrointestinal tract, have been studied. We have evaluated survival of tested FLAB in honey bee gut, their susceptibility to antibiotics (ampicillin, erythromycin, tylosin), cell surface hydrophobicity, auto-aggregation ability, co-aggregation with model pathogenic bacteria, biofilm formation capacity, and effect of studied FLAB, added to sucrose syrup bee diet, on longevity of honey bees. The tested FLAB exhibited good gastrointestinal tract tolerance and high antibiotic susceptibility, which are important criteria in the screening of probiotic candidates. It was also found that all FLAB studied have high cell surface hydrophobicity and fulfil next selection criterion for their use as probiotics. Symbionts of A. mellifera showed also auto- and co-aggregation capacities regarded as valuable features for biofilm formation and inhibition of pathogens adhesion to the bee gut cells. Biofilm-development ability is a desired characteristic of probiotic lactic acid bacteria. As indicated by quantitative crystal violet-stained microplate assay and confocal laser scanning microscopy imaging, all studied A. mellifera gut isolates exhibit a biofilm positive phenotype. Moreover, it was also documented, on honey bees kept in cages, that supplementation of A. mellifera sucrose diet with FLAB decreases mortality and improves significantly longevity of honey bees. Presented research showed that A. mellifera FLAB symbionts are good candidates for application as probiotics.

Effects of Bacterial Supplementation on Black Soldier Fly Growth and Development at Benchtop and Industrial Scale

Historically, research examining the use of microbes as a means to optimize black soldier fly (BSF) growth has explored few taxa. Furthermore, previous research has been done at the benchtop scale, and extrapolating these numbers to industrial scale is questionable. The objectives of this study were to explore the impact of microbes as supplements in larval diets on growth and production of the BSF. Three experiments were conducted to measure the impact of the following on BSF life-history traits on (1) Arthrobacter AK19 supplementation at benchtop scale, (2) Bifidobacterium breve supplementation at benchtop scale, and (3) Arthrobacter AK19 and Rhodococcus rhodochrous 21198 as separate supplements at an industrial scale. Maximum weight, time to maximum weight, growth rate, conversion level of diet to insect biomass, and associated microbial community structure and function were assessed for treatments in comparison to a control. Supplementation with Arthrobacter AK19 at benchtop scale enhanced growth rate by double at select time points and waste conversion by approximately 25–30% with no impact on the microbial community. Predicted gene expression in microbes from Arthrobacter AK19 treatment was enriched for functions involved in protein digestion and absorption. Bifidobacterium breve, on the other hand, had the inverse effect with larvae being 50% less in final weight, experiencing 20% less conversion, and experienced suppression of microbial community diversity. For those tested at the industrial scale, Arthrobacter AK19 and R. rhodochrous 21198 did not impact larval growth differently as both resulted in approximately 22% or more greater growth than those in the control. Waste conversion with the bacteria was similar to that recorded for the control. Diets treated with the supplemental bacteria showed increased percent difference in predicted genes compared to control samples for functions involved in nutritional assimilation (e.g., protein digestion and absorption, energy metabolism, lipid metabolism). Through these studies, it was demonstrated that benchtop and industrial scale results can differ. Furthermore, select microbes can be used at an industrial scale for optimizing BSF larval production and waste conversion, while others cannot. Thus, targeted microbes for such practices should be evaluated prior to implementation.

Extracts from Eleutherococcus senticosus (Rupr. et Maxim.) Maxim. Roots: A New Hope Against Honeybee Death Caused by Nosemosis

Pollinators, the cornerstones of our terrestrial ecosystem, have been at the very core of our anxiety. This is because we can nowadays observe a dangerous decline in the number of insects. With the numbers of pollinators dramatically declining worldwide, the scientific community has been growing more and more concerned about the future of insects as fundamental elements of most terrestrial ecosystems. Trying to address this issue, we looked for substances that might increase bee resistance. To this end, we checked the effects of plant-based adaptogens on honeybees in laboratory tests and during field studies on 30 honeybee colonies during two seasons. In this study, we have tested extracts obtained from: Eleutherococcus senticosus, Garcinia cambogia, Panax ginseng, Ginkgo biloba, Schisandra chinensis, and Camellia sinensis. The 75% ethanol E. senticosus root extract proved to be the most effective, both as a cure and in the prophylaxis of nosemosis. Therefore, Eleutherococcus senticosus, and its active compounds, eleutherosides, are considered the most powerful adaptogens, in the pool of all extracts that were selected for screening, for supporting immunity and improving resistance of honeybees. The optimum effective concentration of 0.4 mg/mL E. senticosus extract responded to c.a. 5.76, 2.56 and 0.07 µg/mL of eleutheroside B, eleutheroside E and naringenin, respectively. The effect of E. senticosus extracts on honeybees involved a similar adaptogenic response as on other animals, including humans. In this research, we show for the first time such an adaptogenic impact on invertebrates, i.e., the effect on honeybees stressed by nosemosis. We additionally hypothesised that these adaptogenic properties were connected with eleutherosides-secondary metabolites found exclusively in the Eleutherococcus genus and undetected in other studied extracts. As was indicated in this study, eleutherosides are very stable chemically and can be found in extracts in similar amounts even after two years from extraction. Considering the role bees play in nature, we may conclude that demonstrating the adaptogenic properties which plant extracts have in insects is the most significant finding resulting from this research. This knowledge might bring to fruition numerous economic and ecological benefits.

Effects on Some Therapeutical, Biochemical, and Immunological Parameters of Honey Bee (Apis mellifera) Exposed to Probiotic Treatments, in Field and Laboratory Conditions

Simple Summary

Various negative factors contribute to a decline in insect pollinators. The aim of this study was to assess the impact of commercial probiotic EM^® PROBIOTIC FOR BEES on honey bees. The study was conducted in field and laboratory-controlled conditions. In the field, the sugar syrup with 10% of probiotic was administered by spraying or feeding the honey bee colonies in order to evaluate the colonies’ strength and Nosema spp. infection levels. In the laboratory, the adult workers have been fed with sugar syrup supplemented with 2.5, 5, and 10% of EM^® for bees for biochemical and immunological analyses of hemolymph, and with 5 and 10% for measuring the size of hypopharyngeal glands. It was found that following the EM^® for bees administration the Nosema spp. spore counts in colonies were significantly reduced, and colonies’ strength was increased. The results at the individual level showed positive physiological changes in treated groups of adult bees, but, at the same time, a higher mortality rate. Our findings indicate that the EM^® for bees is a promising food additive for nosemosis combating. Therefore, additional emphasis needs to be placed on studies investigating the nutritional requirements crucial to improve and sustain honey bee colonies health.

Abstract

Several negative factors contribute to a decline in the number of insect pollinators. As a novel approach in therapy, we hypothesize that the EM^® for bees could potentially have an important therapeutic and immunomodulatory effect on honey bee colonies. The aim of our study was to evaluate its impact on honey bees at the individual and colony level. This is the first appliance of the commercial probiotic mix EM^® PROBIOTIC FOR BEES in honey bees as economically important social insects. The sugar syrup with 10% of probiotic was administered by spraying or feeding the honey bee colonies in the field conditions, in order to evaluate the infection levels with spores of Nosema spp. and colonies’ strength. Moreover, in laboratory-controlled conditions, in the hoarding cages, adult workers have been fed with sugar syrup supplemented with 2.5, 5, and 10% of EM^® for bees for biochemical and immunological analyses of hemolymph, and with 5 and 10% for measuring the size of hypopharyngeal glands. It was found that following the EM^® for bees administration the Nosema spp. spore counts in colonies were significantly reduced, and colonies’ strength was increased. The results at the individual level showed significant positive physiological changes in treated groups of adult bees, revealing at the same time a higher mortality rate when feeding sugar syrup supplemented with the probiotic.

Targeting the honey bee gut parasite Nosema ceranae with siRNA positively affects gut bacteria

BACKGROUND

Gut microbial communities can contribute positively and negatively to host health. So far, eight core bacterial taxonomic clusters have been reported in honey bees. These bacteria are involved in host metabolism and defenses. Nosema ceranae is a gut intracellular parasite of honey bees which destroys epithelial cells and gut tissue integrity. Studies have shown protective impacts of honey bee gut microbiota towards N. ceranae infection. However, the impacts of N. ceranae on the relative abundance of honey bee gut microbiota remains unclear, and has been confounded during prior infection assays which resulted in the co-inoculation of bacteria during Nosema challenges. We used a novel method, the suppression of N. ceranae with specific siRNAs, to measure the impacts of Nosema on the gut microbiome.

RESULTS

Suppressing N. ceranae led to significant positive effects on microbial abundance. Nevertheless, 15 bacterial taxa, including three core taxa, were negatively correlated with N. ceranae levels. In particular, one co-regulated group of 7 bacteria was significantly negatively correlated with N. ceranae levels.

CONCLUSIONS

N. ceranae are negatively correlated with the abundance of 15 identified bacteria. Our results provide insights into interactions between gut microbes and N. ceranae during infection.

Antimicrobial Activity against Paenibacillus larvae and Functional Properties of Lactiplantibacillus plantarum Strains: Potential Benefits for Honeybee Health

Paenibacillus larvae is the causative agent of American foulbrood (AFB), a severe bacterial disease that affects larvae of honeybees. The present study evaluated, in vitro, antimicrobial activity of sixty-one Lactiplantibacillus plantarum strains, against P. larvae ATCC 9545. Five strains (P8, P25, P86, P95 and P100) that showed the greatest antagonism against P. larvae ATCC 9545 were selected for further physiological and biochemical characterizations. In particular, the hydrophobicity, auto-aggregation, exopolysaccharides production, osmotic tolerance, enzymatic activity and carbohydrate assimilation patterns were evaluated. The five L. plantarum selected strains showed suitable physical and biochemical properties for their use as probiotics in the honeybee diet. The selection and availability of new selected bacteria with good functional characteristics and with antagonistic activity against P. larvae opens up interesting perspectives for new biocontrol strategies of diseases such as AFB.

Missing Microbes in Bees: How Systematic Depletion of Key Symbionts Erodes Immunity

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.

Antagonistic Activity against Ascosphaera apis and Functional Properties of Lactobacillus kunkeei Strains

: Lactic acid bacteria (LAB) are an important group of honeybee gut microbiota. These bacteria are involved in food digestion, stimulate the immune system, and may antagonize undesirable microorganisms in the gastrointestinal tract. Lactobacillus kunkeei is a fructophilic lactic acid bacterium (FLAB) most frequently found in the gastrointestinal tracts of honeybees. Ascosphaera apis is an important pathogenic fungus of honeybee larvae; it can colonize the intestine, especially in conditions of nutritional or environmental stress that cause microbial dysbiosis. In this work, some functional properties of nine selected L. kunkeei strains were evaluated. The study focused on the antifungal activity of these strains against A. apis DSM 3116, using different matrices: cell lysate, broth culture, cell-free supernatant, and cell pellet. The cell lysate showed the highest antifungal activity. Moreover, the strains were shown to possess good cell-surface properties (hydrophobicity, auto-aggregation, and biofilm production) and a good resistance to high sugar concentrations. These L. kunkeei strains were demonstrated to be functional for use in "probiotic syrup", useful to restore the symbiotic communities of the intestine in case of dysbiosis and to exert a prophylactic action against A. apis.

Feeding Honeybee Colonies with Honeybee-Specific Lactic Acid Bacteria (Hbs-LAB) Does Not Affect Colony-Level Hbs-LAB Composition or Paenibacillus larvae Spore Levels, Although American Foulbrood Affected Colonies Harbor a More Diverse Hbs-LAB Community

The main current methods for controlling American Foulbrood (AFB) in honeybees, caused by the bacterial pathogen Paenibacillus larvae, are enforced incineration or prophylactic antibiotic treatment, neither of which is fully satisfactory. This has led to an increased interest in the natural relationships between the pathogenic and mutualistic microorganisms of the honeybee microbiome, in particular, the antagonistic effects of Honeybee-Specific Lactic Acid Bacteria (hbs-LAB) against P. larvae. We investigated whether supplemental administration of these bacteria affected P. larvae infection at colony level over an entire flowering season. Over the season, the supplements affected neither colony-level hbs-LAB composition nor naturally subclinical or clinical P. larvae spore levels. The composition of hbs-LAB in colonies was, however, more diverse in apiaries with a history of clinical AFB, although this was also unrelated to P. larvae spore levels. During the experiments, we also showed that qPCR could detect a wider range of hbs-LAB, with higher specificity and sensitivity than mass spectrometry. Honeybee colonies are complex super-organisms where social immune defenses, natural homeostatic mechanisms, and microbiome diversity and function play a major role in disease resistance. This means that observations made at the individual bee level cannot be simply extrapolated to infer similar effects at colony level. Although individual laboratory larval assays have clearly demonstrated the antagonistic effects of hbs-LAB on P. larvae infection, the results from the experiments presented here indicate that direct conversion of such practice to colony-level administration of live hbs-LAB is not effective.

The associations among the breeding performance of Osmia bicornis L. (Hymenoptera: Megachilidae), burden of pathogens and nest parasites along urbanisation gradient

Urban environments may negatively affect the development of organisms. In host-pathogen/parasite systems, this impact may lead to increased manifestations of pathogens that decrease the success of their hosts in urban environments compared to rural ones. We tested this hypothesis in the solitary bee Osmia bicornis L. We estimated the development of bees, their reproductive success and the manifestation of different pathogens and nest parasites along an urbanisation gradient. We conducted the experiment in an urbanisation gradient in sites representing three environments: urban, suburban and rural. First, we analysed the manifestation of bacterial and fungal microorganisms in pollen loads, within dried/mummified individuals, on the surface of cocoons and on the surface of diapausing adult individuals by using the MALDI-TOF MS technique. We also verified genetic samples from diapausing individuals for the presence of the parasitic Nosema apis (Zandler, 1909) and N. ceranae (Fries et al., 1996) species. Finally, we assessed the level of reproductive success and manifestations of brood parasites. Not any biological material from the nests was infected by pathogenic microorganisms. This result indicates that the nests are not a reservoir of the pathogenic bacteria and that O. bicornis offspring are not a source or vectors of these pathogens to the surrounding environment and indirectly to other bee species. In urban sites, there was a lower number of parasites than in suburban and rural environments. The presence of parasites was negatively correlated with the reproductive success and may be a limiting factor for O. bicornis populations. We also found that urban sites had the highest indices of reproductive success and the lowest number of breeding failures compared to suburban and rural sites. Moreover, bacterial and fungal transmission is not a serious threat in the studied region.

Novel probiotic approach to counter Paenibacillus larvae infection in honey 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.

A Pediococcus strain to rescue honeybees by decreasing Nosema ceranae- and pesticide-induced adverse effects

Honeybees ensure a key ecosystemic service by pollinating many agricultural crops and wild plants. However, since few decades, managed bee colonies have declined worldwide. This phenomenon is considered to be multifactorial, with a strong emphasis on both parasites and pesticides. Infection by the parasite Nosema ceranae and exposure to pesticides can contribute to adverse effects, resulting in a perturbation of the honeybee physiology. We thus hypothesized that probiotic treatment could be promising to treat or prevent these disturbances. The aim of this study was to evaluate the effects of probiotics on N. ceranae-infected and intoxicated honeybees (by the insecticide thiamethoxam and the fungicide boscalid). For this purpose, experiments were conducted with five probiotics. Among them, Pediococcus acidilactici (PA) showed the best protective effect against the parasite and pesticides. PA significantly improved the infected honeybee lifespan as prophylactic and curative treatments (respectively 2.3 fold and 1.7 fold). Furthermore, the exposure to pesticides induced an increase of honeybee mortality compared with the control group (p < .001) that was restored by the PA treatment. Despite its beneficial effect on honeybee lifespan, the PA administration did not induce changes in the gut bacterial communities (neither in abundance or diversity). N. ceranae and the pesticides were shown to deregulate genes involved in honeybee development (vitellogenin), immunity (serine protease 40, defensin) and detoxification system (glutathione peroxidase-like 2, catalase), and these effects were corrected by the PA treatment. This study highlights the promising use of PA to protect honeybees from both pathogens and pesticides.

Insect Defense Proteins and Peptides

The composition of insect hemolymph can change depending on many factors, e.g. access to nutrients, stress conditions, and current needs of the insect. In this chapter, insect immune-related polypeptides, which can be permanently or occasionally present in the hemolymph, are described. Their division into peptides or low-molecular weight proteins is not always determined by the length or secondary structure of a given molecule but also depends on the mode of action in insect immunity and, therefore, it is rather arbitrary. Antimicrobial peptides (AMPs) with their role in immunity, modes of action, and classification are presented in the chapter, followed by a short description of some examples: cecropins, moricins, defensins, proline- and glycine-rich peptides. Further, we will describe selected immune-related proteins that may participate in immune recognition, may possess direct antimicrobial properties, or can be involved in the modulation of insect immunity by both abiotic and biotic factors. We briefly cover Fibrinogen-Related Proteins (FREPs), Down Syndrome Cell Adhesion Molecules (Dscam), Hemolin, Lipophorins, Lysozyme, Insect Metalloproteinase Inhibitor (IMPI), and Heat Shock Proteins. The reader will obtain a partial picture presenting molecules participating in one of the most efficient immune strategies found in the animal world, which allow insects to inhabit all ecological land niches in the world.

Current status and application of lactic acid bacteria in animal production systems with a focus on bacteria from honey bee colonies

Lactic acid bacteria (LAB) are widely distributed in nature and, due to their beneficial effects on the host, are used as probiotics. This review describes the applications of LAB in animal production systems such as beekeeping, poultry, swine and bovine production, particularly as probiotics used to improve health, enhance growth and reproductive performance. Given the importance of honeybees in nature and the beekeeping industry as a producer of healthy food worldwide, the focus of this review is on the coexistence of LAB with honeybees, their food and environment. The main LAB species isolated from the beehive and their potential technological use are described. Evidence is provided that 43 LAB bacteria species have been isolated from beehives, of which 20 showed inhibition against 28 species of human and animal pathogens, some of which are resistant to antibiotics. Additionally, the presence of LAB in the beehive and their relationship with antibacterial properties of honey and pollen is discussed. Finally, we describe the use of lactic bacteria from bee colonies and their antimicrobial effect against foodborne pathogens and human health. This review broadens knowledge by highlighting the importance of honeybee colonies as suppliers of LAB and functional food.

The honey bee gut microbiota: strategies for study and characterization

Gut microbiota research is an emerging field that improves our understanding of the ecological and functional dynamics of gut environments. The honey bee gut microbiota is a highly rewarding community to study, as honey bees are critical pollinators of many crops for human consumption and produce valuable commodities such as honey and wax. Most significantly, unique characteristics of the Apis mellifera gut habitat make it a valuable model system. This review discusses methods and pipelines used in the study of the gut microbiota of Ap. mellifera and closely related species for four main purposes: identifying microbiota taxonomy, characterizing microbiota genomes (microbiome), characterizing microbiota-microbiota interactions and identifying functions of the microbial community in the gut. The purpose of this contribution is to increase understanding of honey bee gut microbiota, to facilitate bee microbiota and microbiome research in general and to aid design of future experiments in this growing field.

Honeybee-Specific Lactic Acid Bacterium Supplements Have No Effect on American Foulbrood-Infected Honeybee Colonies

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.

Paenibacillus larvae, the causative agent of American foulbrood (AFB), is the primary bacterial pathogen affecting honeybees and beekeeping. The main methods for controlling AFB are incineration of diseased colonies or prophylactic antibiotic treatment (e.g., with tylosin), neither of which is fully satisfactory. The search for superior means for controlling AFB has led to an increased interest in the natural relationships between the honeybee-pathogenic and mutualistic microorganisms and, in particular, the antagonistic effects of honeybee-specific lactic acid bacteria (hbs-LAB) against P. larvae. These effects have been demonstrated only on individual larvae in controlled laboratory bioassays. Here we investigated whether supplemental administration of hbs-LAB had a similar beneficial effect on P. larvae infection at colony level. We compared experimentally AFB-infected colonies treated with hbs-LAB supplements to untreated and tylosin-treated colonies and recorded AFB symptoms, bacterial spore levels, and two measures of colony health. To account for the complexity of a bee colony, we focused on (Bayesian) probabilities and magnitudes of effect sizes. Tylosin reduced AFB disease symptoms but also had a negative effect on colony strength. The tylosin treatment did not, however, affect P. larvae spore levels and might therefore “mask” the potential for disease. hbs-LAB tended to reduce brood size in the short term but was unlikely to affect AFB symptoms or spores. These results do not contradict demonstrated antagonistic effects of hbs-LAB against P. larvae at the individual bee level but rather suggest that supplementary administration of hbs-LAB may not be the most effective way to harness these beneficial effects at the colony level.

IMPORTANCE 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.

Looking for the causes of and solutions to the issue of honey bee colony losses

Colony losses, including those induced by the colony collapse disorder, are an urgent problem of contemporary apiculture which has been capturing the attention of both apiculturists and the research community. CCD is characterized by the absence of adult dead bees in the hive in which few workers and a queen remain, the ratio between the brood quantity and the number of workers is heavily disturbed in favor of the former, and more than enough food is present. Robbing behavior and pests usually attacking the weakened colony do not occur. In the present paper, the causes of the emergence of this problem are discussed, as well as the measures of its prevention.

The following factors, which lead to colony losses, are analyzed: shortage of high-quality food (pollen and honey); infestation with parasites, primarily with Varroa destructor, and mixed virus infections; bacterial infections (American and European foulbrood), fungal infections (nosemosis and ascosphaerosis) and trypanosomal infections (lotmariosis); and, finally, general management of the apiary.

Certain preventive measures are proposed: (1) providing ample high-quality forage and clean water, (2) avoiding sugarisation, i.e. superfluous use of sugar syrup, (3) meeting the nutritional needs of the colony, (4) when feeding bees, taking care of the timing and the composition of diet, avoiding pure sugar syrup which in excessive quantities may induce energetic and oxidative stress, (5) when there is a shortage of natural feed – honey in the brood chamber – use sugar syrup with natural/artificial supplements to avoid protein starvation, (6) organized control of V. destructor in the colonies is obligatory due to its vector role, and (7) compliance with hygienic and sanitary measures and principles of good apiculture practice and management in apiaries. To conclude, all preventive measures are feasible in compliance with rules and regulations concerning regular spring and autumn bee health monitoring by licensed veterinarians, who can propose adequate treatments if necessary.

Scientific Advances in Controlling Nosema ceranae (Microsporidia) Infections in Honey Bees (Apis mellifera)

Honey bees (Apis mellifera) are agriculturally important pollinators that have been recently at risk to severe colony losses. A variety of parasites and pathogens have been linked to colony decline, including the microsporidian parasite Nosema ceranae. While fumagillin has been used to control nosemosis in managed honey bee colonies for decades, research shows that this antibiotic poses a toxic threat and that its efficacy against N. ceranae is uncertain. There is certainly a demand for a new veterinary medication to treat honey bee colonies infected with N. ceranae. In this review, recent scientific advances in controlling N. ceranae infections in honey bees are summarized.

Gram-Positive Bacteria with Probiotic Potential for the Apis mellifera L. Honey Bee: The Experience in the Northwest of Argentina

Apis mellifera L. is one of the most important natural pollinators of significant crops and flowers around the world. It can be affected by different types of illnesses: american foulbrood, nosemosis, varroasis, viruses, among others. Such infections mainly cause a reduction in honey production and in extreme situations, the death of the colony. Argentina is the world's second largest honey exporter and the third largest honey producer, after China and Turkey. Given both the prominence of the honey bee in nature and the economic importance of apiculture in Argentina and the world, it is crucial to develop efficient and sustainable strategies to control honey bee diseases and to improve bee colony health. Gram-positive bacteria, such as lactic acid bacteria, mainly Lactobacillus, and Bacillus spp. are promising options. In the Northwest of Argentina, several Lactobacillus and Bacillus strains from the honey bee gut and honey were isolated by our research group and characterized by using in vitro tests. Two strains were selected because of their potential probiotic properties: Lactobacillus johnsonii CRL1647 and Bacillus subtilis subsp. subtilis Mori2. Under independent trials with both experimental and commercial hives, it was determined that each strain was able to elicit probiotic effects on bee colonies reared in the northwestern region of Argentina. One result was the increase in egg-laying by the queen which therefore produced an increase in bee number and, consequently, a higher honey yield. Moreover, the beneficial bacteria reduced the incidence of two important bee diseases: nosemosis and varroosis. These results are promising and extend the horizon of probiotic bacteria to the insect world, serving beekeepers worldwide as a natural tool that they can administer as is, or combine with other disease-controlling methods.

The Role of Prebiotics and Probiotics in Gastrointestinal Disease

With the advent of the scientific realization that the microbiota of the gastrointestinal tract was more than the cells that exist in the body, the full importance of prebiotics and probiotics has come forth. The importance has been stressed and is available in the new textbook entitled, "The Microbiota in Gastrointestinal Pathophysiology: Implication for Human Health, Prebiotics, Probiotics and Dysbiosis." There is enough evidence now published in the literature so that the scientific world now believes that prebiotics and probiotics are important in gastrointestinal disease.

Effect of gut bacterial isolates from Apis mellifera jemenitica on Paenibacillus larvae infected bee larvae

The probiotic effects of seven newly isolated gut bacteria, from the indegenous honey bees of Saudi Arabia were investigated. In vivo bioassays were used to investigate the effects of each gut bacterium namely, Fructobacillus fructosus (T1), Proteus mirabilis (T2), Bacillus licheniformis (T3), Lactobacillus kunkeei (T4), Bacillus subtilis (T5), Enterobacter kobei (T6), and Morganella morganii (T7) on mortality percentage of honey bee larvae infected with P. larvae spores along with negative control (normal diet) and positive control (normal diet spiked with P. larvae spores). Addition of gut bacteria to the normal diet significantly reduced the mortality percentage of the treated groups. Mortality percentage in all treated groups ranged from 56.67% up to 86.67%. T6 treated group exhibited the highest mortality (86.67%), whereas T4 group showed the lowest mortality (56.67%). Among the seven gut bacterial treatments, T4 and T3 decreased the mortality 56.67% and 66.67%, respectively, whereas, for T2, T6, and T7 the mortality percentage was equal to that of the positive control (86.67%). Mortality percentages in infected larval groups treated with T1, and T5 were 78.33% and 73.33% respectively. Most of the mortality occurred in the treated larvae during days 2 and 3. Treatments T3 and T4 treatments showed positive effects and reduced mortality.

Impact of beneficial bacteria supplementation on the gut microbiota, colony development and productivity of Apis mellifera L

Honey bees are important pollinators of several crops and ecosystems, having a great ecological and economic value. In Europe, the restricted use of chemicals and therapeutic agents in the beekeeping sector has stimulated the search for natural alternatives with a special focus on gut symbionts. The modulation of the gut microbiota has been recognised as a practical and successful approach in the entomological field for the management of insect-related problems. To date, only a few studies have investigated the effect of bacterial supplementation on the health status of colonies, colony productivity and gut symbionts. To this purpose, a preparation of sugar syrup containing bifidobacteria and lactobacilli isolated from bee gut was sprayed on the frames of an apiary located in open field once a week for four weeks. Treated and control hives were monitored for two months for brood extension, honey and pollen harvest. The presence of beneficial gut microorganisms within bee gut was investigated with denaturing gradient gel electrophoresis and next generation sequencing. The administered bacteria led to a significant increase of brood population (46.2%), pollen (53.4%) and harvestable honey in honey supers (59.21%). Analysis of the gut microbiota on the new generation of bees in treated hives showed an increase in relative abundance of Acetobacteraceae and Bifidobacterium spp., which are known to be involved in bee nutrition and protection.