The makeup of microbial species — the microbiome — in the gut of a honeybee queen changes slowly as she ages, while a worker bee’s microbiome changes much more rapidly, according to a new study published by researchers with the U.S. Department of Agriculture's Agricultural Research Service (ARS).

Learning the details of the honeybee gut microbiome offers potential for a whole new set of tools for managing honeybee colonies, explained ARS microbial ecologist Kirk E. Anderson at the Carl Hayden Bee Research Center in Tucson, Ariz.

“We established the close connection of the makeup of the honeybee microbiome with the physiology of aging and stress. Our results provide a roadmap to improving colony health through improving queen rearing, nutrition and other management practices,” he explained.

Honeybee queens, which lay all of the eggs in a hive, commonly last about three years in managed colonies before their reproduction slows and beekeepers replace them, ARS said. However, in recent years, queens have been failing more quickly. This is a factor in higher colony losses reported during the past 12 years and has increased beekeepers’ costs and labor, according to ARS. Queens currently cost about $25 each.

The honeybee gut microbiome plays a significant role in metabolism, development and growth and immune system function and protection against pathogens, ARS noted. From among a common list of 10-12 bacterial species groups, five to seven species groups usually make up the vast majority of a honeybee’s core microbiome. The exact mix depends on a honeybee’s age and function in the hive.

Anderson and ARS molecular biologist Vincent Ricigliano found that as a queen ages, the levels of two bacterial species groups in her gut microbiome slowly increase: Lactobacillus and Bifidobacterium, both known for providing probiotic benefits in mammals, including people. At the same time, her microbiome has decreased levels of Proteobacteria species, which are often associated with unhealthy microbial imbalances.

The rate of this shift is associated more with a queen’s biological age than her chronological age, ARS said, explaining that queens age biologically at different rates depending on their colony’s exposure to a variety of environmental stresses, which can include available nutrition and temperature extremes.

Interestingly, according to the announcement, during this study, the researchers discovered a new potentially queen-specific pathogen that was not detected in any adult worker bees: Delftia bacteria (in the order Burkholderiales). The occurrence of Delftia in the queen’s mouth and gut rose or fell opposite the levels of bacteria considered beneficial. This suggests that Delftia may play a part in early queen mortality, according to Anderson.

In comparison, as worker bees aged, Lactobacillus and Bifidobacterium levels dropped, and the number of Proteobacteria went up, ARS said. Workers’ microbiomes appear to change in a highly predictable fashion, especially with age. This may mean that early shifts in worker bee microbiota could be used as a warning indicator for colony dwindling and/or failure.

Applying this new information to enhance the microbiome of honeybees may represent a new strategy to slow their aging or to combat physiological stress, ARS said.

In addition, as the understanding of the honeybee’s relatively straightforward microbiome increases, the ARS researchers are hopeful that bees could become an excellent model in which to study the much more complex microbiome of other species, including people.