Pollen reverses decreased lifespan, altered nutritional metabolism, and suppressed immunity in honey bees (Apis mellifera) treated with antibiotics

Authors: LI, JIANGHONG - Fujian Agricultural & Forestry University; Heerman, Matthew; Evans, Jay; LI, WENFENG - Zhejiang University; RODRIGUEZ-GARCIA, CRISTINA - Non ARS Employee; DeGrandi-Hoffman, Gloria; ZHAO, YAZHOU - Chinese Academy Of Agricultural Sciences; HUANG, SHAOKANG - Fujian Agricultural & Forestry University; LI, ZHIGUO - Fujian Agricultural & Forestry University; Hamilton, Michele; Chen, Yanping - Judy

Submitted to: Journal of Experimental Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/25/2019
Publication Date: 3/7/2019
Citation: Li, J., Heerman, M.C., Evans, J.D., Li, W., Rodriguez-Garcia, C., Hoffman, G.D., Zhao, Y., Huang, S., Li, Z., Hamilton, M.C., Chen, Y. 2019. Pollen reverses decreased lifespan, altered nutritional metabolism, and suppressed immunity in honey bees (Apis mellifera) treated with antibiotics. Journal of Experimental Biology. 222:jeb202077. https://doi.org/10.1242/jeb.202077.
DOI: https://doi.org/10.1242/jeb.202077

Interpretive Summary: Gut microbes have a significant role in food digestion and immune functions. And in turn, the food can drive changes in the composition and diversity of gut microbes. The interactions of diet-microbiota can profoundly impact many aspects of animal health. In the present study, we evaluated the effects of gut bacteria disruption by antibiotics on the honey bees' immunity, nutrient metabolism, head weight, and survival rate. We observed that gut bacteria disruption resulted in a decrease in the expression of genes normally involved in nutrient metabolism and immune functions and an increase in Deformed wing virus replication activity. While antibiotics caused a significant drop in honey bee physiological functions and survivorship, the effects could be rescued by addition of pollen to diets. Our results provide a deeper understanding of the interconnections among gut bacteria, nutrition and immunity in honey bees and should be of interest to the researchers, graduate students, apiary inspectors, and beekeepers worldwide.

Technical Abstract: Nutrition is involved in regulating multiple aspects of honeybee biology such as caste, immunity, lifespan, growth and behavioral development. Deformed wing virus (DWV) is a major pathogenic factor which threatens honeybee populations, and its replication can be negatively impacted by sufficient nutrition and immune responses generated by honeybees. The alimentary canal of the honeybee is home to a diverse microbial community that synthesize essential nutrients from food and serves to bolster immune responses. However, to what extent gut bacteria affect honeybee nutrition metabolism and immunity with respect to DWV has not been investigated fully. In this study, newly emerged worker bees were subjected to four diets that contained pollen, pollen and antibiotics, antibiotics alone, or 50% sucrose solution and neither pollen or antibiotics. The expression level of two nutrition genes target of rapamycin (tor) and insulin like peptide (ilp1), one physiological and nutritional marker gene vitellogenin (vg), five major royal jelly proteins genes (mrjp1-5), one antimicrobial peptide regulating gene relish (rel), and DWV virus titer and its negative replication strand were determined by qRT-PCR from the honeybees after 7 days post treatment. Additionally, honeybee head weight and their survival rate were measured. We observed that antibiotics decreased the expression of tor and rel, increased DWV titer and its replication activity. Expression of ilp1, five mrjps, vg, and honeybee head weight were also reduced compared to bees on a pollen diet. Antibiotics also caused a significant drop in survivorship, which could be rescued by addition of pollen to diets. Of importance, pollen could partially rescue the loss of vg and mrjp2 while also increasing head weight of antibiotic treated bees. Our results illuminate the roles of pollen and gut bacteria in honeybee nutrition, metabolism, and immunity; which confer the capability of inhibiting virus replication, extending honeybee lifespan and improving overall health.