Queen bee microbiome distinct from worker bees

Bees are essential to agriculture because of their role in pollination. Recent concerns about declining bee populations, especially that of the European honey bee, Apis mellifera, has increased researchers’ interest in the microbiome of the honey bee. The microbial composition of worker bees, as well as the queen-rearing process, is well known, but little to nothing is known about the queen bee microbiome. Researchers from North Caroline State University, Wellesley College, and Indiana University analyzed the queen bee microbiome composition at different stages of development, and compared their findings to the worker bee microbiome composition.  Their results were recently published in Applied and Environmental Microbiology.

 At North Caroline State University’s Lake Wheeler Honey Bee Research Facility a single honey bee colony was chosen as the source of all queen bees used in this experiment, with the purpose of eliminating genetic variance as a variable. The queen bees had their gut microbiomes tested at five different stages of development: larvae, newly emerged queens, maturing queens in the mating nucleus, and laying queens both before and after their offspring emerged.

 Drastic changes in the microbiome composition occurred during the maturation of queen bees, with the largest changes occurring between young queens (larvae and the newly emerged adults) and mature queens.  The scientists speculated that these changes occurred because during maturation the queens begin to physically contact worker bees. To test this, the researchers characterized the microbiome of worker bees that may have helped rear the queens. The worker bees exhibited a similar communal microbiome, while the queen bees appeared the lack this microbiome; instead they showed a predominance of α-proteobacteria. In fact, there was greater variability among related queen bees than there was among unrelated worker bees. The scientists think this may be because of the communal environment that worker bees are exposed to, from which queen bees are carefully secluded.

 The main question here is where do the queen bees get their microbial characteristics from? Human’s and other mammals’ microbiomes are greatly influenced by the mother during the birthing process. Conversely, queen bees appear to develop their microbiome because of the “royal jelly” they are carefully fed during development, which comes from the hypopharyngeal glands of nurse worker bees, and because of the care worker bees take in keeping the queen’s environment clean by grooming and disposing of her fecal matter.

 The most significant finding from this study is that the queen bee’s microbiome does not reflect the specific microbial community of her worker bees. This may not seem important to a non-beekeeper, but to someone who works with bees this means that the movement of queen bees from one colony to another should not disrupt the microbiome, and therefore the health of the workers. This is good news to beekeepers and those in the agriculture business who are concerned with the health of their bee populations, especially in light of the recently declining bee population. 

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