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.

蜜蜂（Apis mellifera）的肠道微生物群对于个体和群体层面的健康至关重要。健康的肠道微生物群与中心代谢紧密相连，提供对病原体的防护，协助解毒，并激活免疫系统。在工蜂群体中，基于年龄的多神论决定了劳动分工，这对群体的成功亦至关重要。无论年龄如何，蜜蜂工蜂可以根据群体的需求承担各种生理/行为角色。我们研究了工蜂年龄结构对回肠和直肠（后肠）微生物群的影响，特别是我们迫使觅食者回归到育儿行为；这一行为与年轻生理状态相关。我们假设重复摄入花粉会导致氧化应激和微生物群的改变。我们发现，核心后肠微生物群相对稳定，但两种假定的机会性细菌因处理方式不同而有所差异。与回归觅食者中前列腺素氧化酶（PPO）表达增加相关，我们观察到中肠中憩室的形成，这表明肠道完整性的丧失。总体而言，我们的研究结果表明后肠微生物群的稳定性，但中肠随年龄增长而衰老，回归现象使蜜蜂易受败血症的侵袭。