Location: Honey Bee Research2012 Annual Report
1a. Objectives (from AD-416):
1: Determine the nutrients in pollen that promote worker longevity. 1.A. Determine the effects of pollen mixtures on worker protein and lipid stores and longevity. 1.B. Characterize the chemical composition of pollen mixtures that optimize worker protein and lipid stores and longevity. 2: Determine the effects of undigested saccharides in high fructose corn syrup (HFCS) on worker physiology and longevity. 2.A. Identify the saccharides in HFCS. 2.B: Determine the effect of saccharides in HFCS on worker physiology and longevity. 3: Evaluate the effects of supplemental feeding on Varroa tolerance, queen production and foraging activity of honey bee colonies. 3.A. Modify the MegaBee diet by adding chemical components that were identified in the pollen mixture analysis. 3.B. Determine the effects of nutrition on Varroa infestation and reproduction in worker and drone cells. 3.C. Determine the role of nutrition on queen production and reproductive potential. 3.D. Evaluate the effects of supplemental protein feeding on the foraging rates of honey bee colonies. 3.E. Improving honey bee immune response to CCD by determining the role of symbiotic microbes in bee nutrition.
1b. Approach (from AD-416):
1. Nutritional value will be evaluated by measuring protein and lipid levels and on bee longevity. The chemical composition of pollens that are more nutritious than MegaBee will be determined. 2. Determine the effects of high fructose corn syrup containing higher saccharides on honey bee longevity. 3. Determine the effects of improved nutrition of the longevity of bees parasitized by Varroa, the reproductive potential of queens, and foraging activity of colonies used for pollination.
3. Progress Report:
We are in the final year of our 5-year plan with only sub-objectives under objective 3 remaining. ARS researchers in Tucson, AZ, made progress on understanding the role of nutrition in maintaining colony health by studying the effects of diet on the growth of parasitic Varroa mite populations, queen rearing, and gene expression in nurse bees. We also identified biomarkers associated with nutritional stress. Microbial communities associated with nutrient acquisition also were identified, and their role in digestion and immunity is being discerned. Under sub-objective 3b, we found that infestation levels and reproductive rates of Varroa were affected by diet. Brood from colonies fed pollen or from open foraging colonies had lower mite levels than colonies fed a supplemental protein diet. A second replicate of this study is underway to determine if results can be repeated. Pollen collected by honey bees often is contaminated with fungicides and pesticides. Under sub-objective 3c, we found that queen rearing was negatively affected when colonies were fed pollen contaminated with a commonly used pesticide alone and in combination with a fungicide. The percentage of queens that were reared to emergence was reduced and those that emerged had incidence of virus compared with queens reared in colonies without pesticide contamination. These results are underscored by findings that nutrition affects the expression of genes in nurse bees that are associated with immunity, protein breakdown and metabolic pathways. Under sub-objective 3d, we found that chronically-malnourished colonies that were completely dependent on supplemental protein diets had lower levels of ß-ocimene, a volatile compound associated with brood and egg laying by queens. The decline was associated with cannibalism of young larvae by adult workers. Subsequent examination of nutrient stores in developing young adult workers revealed that their protein stores were much lower in the pollen-deprived colonies than the pollen-fed colonies. When pollen feeding was resumed, both brood and ß-ocimene production increased. These results underscore the importance of feeding pollen to nutritionally-stressed colonies and further demonstrate the limitations of feeding protein supplements for extended periods. An important difference between pollen and protein supplements is the lack of beneficial microbes that honey bees acquire from collecting nectar and pollen. Studies conducted under sub-objective 3e showed that the most abundant bacteria found in stored pollen and the honey bee’s crop are typically found in the pollination environment or floral nectar. A subset of these bacteria might play a role in preserving pollen, converting it to beebread, inhibiting pathogens, and providing amino acids and other nutrients through metabolic activities. Our study on the protein and amino acid content of pollen before and after it was converted to bee bread showed lower protein levels and higher amino acid concentrations in the bee bread in most instances. These changes might be due to microbial activity during the making of bee bread that cannot be duplicated in protein supplements.
1. Gut microbiota of honey bee larva were isolated and sequenced. In honey bee colonies, larvae are fed pollen and a proteinaceous secretion called worker jelly that is made by nurse bees. During feeding, microbes are passed between adult bees and larvae. ARS researchers at the Carl Hayden Bee Research Center in Tucson, Arizona,investigated the overall distribution and abundance of gut bacteria in larvae of different ages and isolated and sequenced approximately 300 bacterial samples from larvae. One of the core bacteria (Alpha 2.2) has an intermittent presence in adults, but dominates the larval gut community. The growth of Alpha 2.2 is enhanced in dilute honey or larval food (royal or worker jelly). The isolation and genome sequence of these bacteria can provide the basis for determining their function in larval nutrition and immunity.
2. Gut microbiota increases larval survival in pathogen challenged honey bees. Honey bee larvae are targets for many pathogens, and because of the social environment in colonies, disease outbreaks can quickly become fatal epidemics. Honey bees evolved with communities of microbes, many of which likely prevent the growth of pathogenic bacteria and fungi. ARS scientists at the Carl Hayden Bee Research Center in Tucson, Arizona, and the University of Arizona investigated the role of gut microbiota in suppression of fungal pathogens of honey bee larvae. The larvae were reared outside the colony environment with and without their normal gut microbiota. When the larvae were exposed to the fungal pathogen that causes chalkbrood disease, larvae that were fed core gut microbiota were able to reduce the growth of the pathogenic fungus and survived longer than did larvae without the core microbiota. These results indicate that the microbiota in healthy larvae can reduce the growth of chalkbrood and possibly other common brood diseases.
3. Effects of sublethal exposure of pesticides on queen rearing and virus titers. Honey bees often are exposed to pesticides and fungicides when colonies are in agricultural areas, and these contaminants often are found in pollen collected by honey bees. When ARS researchers at the Carl Hayden Bee Research Center in Tucson, Arizona, fed queen rearing colonies pollen contaminated with a pesticide alone (chlorpyrifos) and with the addition of a fungicide, fewer queens were reared to emergence than when reared in colonies without contaminated pollen. Collaborators at the ARS Beltsville Bee Lab found that those queens that did emerge had higher incidence of virus when they were reared in colonies fed pollen contaminated with an insecticide alone or in combination with a fungicide. Our study indicates that sublethal levels of contaminated pollen fed to queen rearing colonies could hamper commercial queen production and natural colony re-queening, which could cause colony loss. The study also indicates that the queens that do emerge carry virus that might shorten their lives and in some instances be transferred through their eggs to their offspring.
4. Beneficial bacteria shared between the pollination environment and the stored food of honey bees (Apis mellifera). Symbiotic microbes are essential for preserving pollen in the hive and converting it to a nutritious fermented food called bee bread. ARS researchers at the Carl Hayden Bee Research Center in Tucson, Arizona, determined that the most abundant bacteria found in stored pollen and in the honey bees’ crop are also found in flowers. Our findings suggest that a subset of these bacteria is responsible for preserving bee bread and inhibiting the growth of pathogens in the colony. The results are important for understanding the role that microbes collected with nectar and pollen have in food processing and nutrient acquisition in the colony. The results also indicate that colony health and susceptibility to disease might be affected by environmental contaminants that inhibit the presence or growth of these beneficial microbes.
5. Changes in nutritional value of pollen after its conversion to bee bread. Honey bees meet most of their nutritional requirements by collecting pollen, and converting it to a fermented honey and pollen mixture called bee bread. The nutritional value of pollen often is evaluated by the presence and concentration of essential amino acids. ARS researchers at the Carl Hayden Bee Research Center in Tucson, Arizona, used two genetically different races of honey bees, European (EHB) and African (AHB) to determine if there were changes in the nutritional value of pollen once it became bee bread and whether the changes were affected by colony genetics. We found that the protein concentration in the bee bread made by either race was significantly lower than in the pollen and that in general, amino acid concentrations were higher. There were differences in amino acid concentrations between bee bread made by EHB and AHB. Our study indicates that the nutritional value of pollen should be evaluated after its conversion to bee bread because protein and amino acid levels can change greatly during the fermentation process.
Hoffman, G.D., Eckholm, B., Anderson, K.E. 2012. Honey bee health: The potential role of microbes. In: Sammataro, D. and Yoder, J., editors. Honey Bee Colony Health: Challenges and Sustainable Solutions. Boca Raton, FL. CRC Press. p. 1-12.