Agriculture - - Research - BY KIM KA­PLAN

TUC­SON, ARI­ZONA – The makeup of mi­cro­bial species—the mi­cro­biome—in a honey bee queen’s gut changes slowly as she ages, while a worker bee’s mi­cro­biome changes much more rapidly, ac­cord­ing to a new study pub­lished by Agri­cul­tural Re­search Ser­vice (ARS) sci­en­tists.

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

“We es­tab­lished the close con­nec­tion of the makeup of the honey bee 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.

Honey bee queens, which lay all of the eggs in a hive, com­monly last about three years in man­aged colonies be­fore bee­keep­ers re­place them as re­pro­duc­tion slows. But 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. Queens cur­rently cost about $25 each.

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

An­der­son and ARS molec­u­lar bi­ol­o­gist Vin­cent Ri­cigliano found that as a queen ages, in her gut mi­cro­biome, the lev­els of two bac­te­rial species groups slowly in­crease: Lac­to­bacil­lus and Bi­fi­dobac­terium, both known for pro­vid­ing pro­bi­otic ben­e­fits in mam­mals in­clud­ing hu­mans. 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. Queens age bi­o­log­i­cally at dif­fer­ent rates de­pend­ing on their colony’s ex­po­sure to a va­ri­ety of en­vi­ron­men­tal stresses, which can in­clude avail­able nu­tri­tion and ex­po­sure to tem­per­a­ture ex­tremes.

In­ter­est­ingly, dur­ing this study, the re­searchers dis­cov­ered a new po­ten­tially queen-spe­cific pathogen 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 to the lev­els of bac­te­ria con­sid­ered ben­e­fi­cial. This sug­gests Delf­tia may play a part in early queen mor­tal­ity, ac­cord­ing to An­der­son.

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

Ap­ply­ing this new in­for­ma­tion to en­hanc­ing honey bees’ mi­cro­biome may rep­re­sent a new strat­egy to slow their aging or to com­bat phys­i­o­log­i­cal stress.

In ad­di­tion, as un­der­stand­ing of the honey bee’s rel­a­tively straight­for­ward mi­cro­biome in­creases, the ARS re­searchers are hope­ful that bees may of­fer an ex­cel­lent model in which to study the much more com­plex mi­cro­biome of other species in­clud­ing hu­mans. (AGRI­CUL­TURAL RE­SEARCH SER­VICE)

In gen­eral, honey bee health has been de­clin­ing since the 1980s, with the introduction of new pathogens and pests. (Photo by Rob Flynn)

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