Bee-Microbiota Relationship Unveiled: Bees Synthesize Food for Gut Bacteria

Bacteria, with their remarkable adaptability, have found a home in various terrestrial environments, including the guts of animals. In this intimate association, they play crucial roles such as aiding digestion, regulating the immune system, protecting against pathogens, and even influencing their host's behavior and cognition. While the benefits to the host are well-established, a recent study focused on the western honey bee (Apis mellifera) explores the reciprocity in this relationship. Conducted by researchers at the University of Lausanne (UNIL), the study sheds light on how bees might actively contribute to the nutrition of their gut bacteria, unveiling a fascinating aspect of the bee-microbiota relationship.

Known for their honey production, honey bees serve as an excellent model for gut microbiota research due to their relatively simple and stable microbiota composed of around twenty bacterial species. Professor Philipp Engel and his team at UNIL's Department of Fundamental Microbiology chose bees as a model system to investigate whether bees play an active role in providing nutrients to their gut bacteria.

The study, published in Nature Microbiology, focused on bees that were raised without any gut bacteria and subsequently fed specific bacterial species to colonize their guts. To understand how the bees' diet influenced the bacteria, researchers, including Dr. Andrew Quinn and Ph.D. candidate Yassine El Chazli, initially investigated if bacteria shared nutrients when bees were given a diet of only sugar water.

Surprisingly, one specific bacterium, Snodgrassella alvi, was found to colonize the bee gut even when sugar water was the sole food source. Intriguingly, S. alvi cannot metabolize sugar to grow. The researchers hypothesized that the bee might be directly providing the necessary nutrients for S. alvi to colonize its gut.

To test this hypothesis, the researchers collaborated with Professor Anders Meibom's team, experts in measuring metabolite flux at the nanometer scale using NanoSIMS technology. Bees with a microbiota-free gut were fed a special diet of glucose where carbon isotopes were replaced. After colonizing these bees with S. alvi, the researchers used NanoSIMS to create a 2D image of the bee's gut, showing the enrichment of the isotopes in S. alvi cells.

The results conclusively demonstrated that bees synthesize multiple acids, exported into the gut, which serve as nutrients for S. alvi. The collaborative effort between UNIL and EPFL showcased the power of interdisciplinary scientific collaboration, offering insights into the intricate metabolic synergy between bees and their gut bacteria.

The findings could have broader implications, potentially explaining why bees possess such a specialized and conserved gut microbiota. Moreover, these mechanisms might contribute to understanding bees' vulnerability to climate change, pesticides, and new pathogens. The researchers are now investigating how disruptions in this metabolic synergy might impact bees and seeking answers to pressing questions about the effects of factors like glyphosate exposure on bee health.

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