The effect of social reversion on the honey bee (Apis mellifera) hindgut microbiota

The honey bee (Apis mellifera) gut microbiome is integral for individual and colony-level health. A healthy gut microbiome is tied to central metabolism, provides protection from pathogens, aids in detoxification, and primes the immune system. Among the worker caste, age-based polytheism dictates the division of labor and is also integral to colony success. Independent of age, the honey bee worker can assume various physiological/behavioral roles based on colony needs. We investigated the disruption of worker age demographics on the ileum and rectum (hindgut) microbiomes, specifically, we forced foragers to revert to nursing; a task associated with youthful physiology. We hypothesized that the repeated consumption of pollen would result in oxidative stress and alterations to the microbiota. We found that the core hindgut microbiome remained relatively stable, with the exception of two putative opportunistic bacteria that differed by treatment. Associated with increased expression of prophenoloxidase (PPO) in reverted foragers, we observed the formation of diverticula in the midgut suggesting a loss of gut integrity. Collectively, our results suggest stability of the hindgut microbiome, but senescence of the midgut with reversion phenotypes becoming susceptible to septicemia.