Researchers have published the first comprehensive analysis of the gut bacteria found in queen honey bees (Apis mellifera), and they’ve found that the microbiomes of queens are very different from worker bee microbiomes.
“In many animals, transmission of the microbiome is maternal,” said co-author Irene L.G. Newton, assistant professor of biology at the Indiana University. “In the case of the honey bee, we found that the microbiome in queen bees did not reflect those of worker bees — not even the progeny of the queen or her attendants. In fact, queen bees lack many of the bacterial groups that are considered to be core to worker microbiomes.”
The study’s results, which are published in the journal Applied and Environmental Microbiology, are the opposite of microbiome development in many mammals, in which infants’ microbiomes are influenced by their mothers. Human babies delivered through natural birth possess microbiomes similar to those found in their mother’s birth canal, for example, while babies born through cesarean section harbor gut bacteria that resemble bacteria found on the skin.
Honey bees, in contrast, acquire their gut bacteria from both the surrounding environment and their social context — a phenomenon known as horizontal transmission. In a healthy colony, worker bees typically acquire their gut bacteria through interaction with microbes inside the hive, including fecal matter from adult bees. But the most likely route of microbiome transmission in queen bees is the “royal jelly,” a protein-rich food source produced by worker bees that is responsible for the development of queen bees during the larval stage. Unlike other bees, queens continue to feast on royal jelly through maturity, instead of the honey and “bee bread” that is consumed by workers.
The queen’s royal isolation from the dirt and grime of everyday life in the colony may account for the difference in her microbiome.
“In some ways, the development of the queen microbiome mirrors that of workers, with larval queens’ associated bacteria resembling those found in worker larvae,” Newton said. “But, by the time they mature, queens have developed a microbial signature distinct from the rest of the colony.”
Newton’s study tracked the development of the queen microbiome at every point in the commercial rearing process — from the larval stage to their emergence as adults capable of reproduction. The scientists also tracked worker populations interacting with the queens at each point in their development, including the queens’ introduction to new colonies, a common practice in commercial beekeeping. At the end of the process, DNA collected from the honey bees’ guts were sequenced and analyzed.
The study’s discovery that a queen bee’s microbiome remains unaffected by her interactions with workers, and by the movement of queens to different colonies, suggests that modern beekeeping practices — in which queen bees are regularly removed from their home colonies and introduced into new hives — may not detrimentally affect the health of the colony.
“Because the queen microbiome does not reflect the workers within a specific colony, the physical movement of queens from one colony environment to another does not seem to have any major effects on either the queen gut or worker gut communities,” Newton said. “The research provides no evidence that beekeepers who regularly replace their queens from outside genetic sources harm their colonies by disrupting the gut microfauna of a particular colony. In many ways, these conclusions are very reassuring for the commercial-production apiculture industry.”
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