Investigations into the comparative role of hydrogen peroxide in social bees and links to nutritional stress

Infectious disease is a challenge for eusocial insects living in large social groups, resulting in a plethora of defensive mechanisms. One example is the production of hydrogen peroxide (H2O2) within honey stores. H2O2 is synthesized by honeybee (Apis mellifera) production of glucose oxidase (GOX) and maintained within honey stores at varying concentrations as a proactive defense against microbial growth. Despite the high cost of H2O2 production and tolerance of the subsequent oxidative stress from consumption, it is a constitutive part of the honeybee social immunity response though it remains little investigated and the extent of its application, as well as the factors impacting production, are currently unclear.
The vital role nutrition plays in honeybee physiology and defense suggests it is an important factor for consideration in GOX production. Evidence indicates that unlike sucrose solution, high fructose corn syrup (HFCS) provided during nectar dearth suppresses GOX production. We are therefore investigating the link between sugar feed and immunity, health, and survival to better understand how management choices affect honeybee and bumblebee (Bombus impatiens) colony diseases and wider health, specifically whether production and use of GOX and subsequent colony-level pathogen defense is influenced by supplemental sugar feeds. Analysis of H2O2 content in honeybee honey samples has revealed reduced H2O2 content in colonies supplementarily fed HFCS compared to sucrose or unfed colonies, supporting the importance of nutrition in colony defense. We expect to see similar patterns in bumblebee honey and comparative analyses may reveal an evolutionary link in social immunity between the species.