A honeybee hive is a pantry worth raiding — packed with pollen and honey — so it needs good security. A new study suggests part of that security detail may come straight from flowers: tiny bacteria that make natural antibiotics and hitch a ride back to the hive on pollen.
The suspects here are endophytes — friendly microbes that live inside plants. When bees dust themselves with pollen, they may pick up these helpers and carry them home, researchers in the US report. “We found that the same beneficial bacteria occur in pollen stores of honeybee colonies and on pollen of nearby plants,” said Daniel May of Washington College.
In the lab and out in the field, the team looked for actinobacteria, a family famous for supplying many of our medical antibiotics. They sampled pollen from 10 native plant species at a nature preserve in Wisconsin and from the pollen stores of a nearby hive. The same cast kept showing up in both places, with most isolates belonging to Streptomyces — a group known for brewing potent antimicrobial compounds.
Then came the key question: could these flower-picked microbes actually fend off bee germs? The researchers grew the isolates next to known bee pathogens to see if the newcomers would block their growth. Many did.
The fungus Aspergillus niger, which can cause a bee disease called stonebrood, was strongly suppressed. Some strains also slowed or stopped troublesome bacteria, including Paenibacillus larvae, the culprit behind the devastating brood disease American foulbrood, and Serratia marcescens. Several of the same strains held their own against plant pathogens, too.
“We also show that these bacteria produced similar antimicrobial compounds that kill pathogens of bees and plants, making them a great starting point for new treatments of crops and hives,” May says.
Genetic clues backed up the story: the isolates carried telltale code used by plant-dwelling microbes and the machinery to make antibiotic-like molecules. In plain terms, they looked and behaved like plant partners — and useful ones.
The path they take from petal to pantry seems straightforward. “We isolated the same Streptomyces bacteria from flowers, pollen-covered bees leaving flowers, and hives. We conclude from our results that endophytic actinobacteria on pollen grains are picked up by pollinating bees and whisked back to hive pollen stores, where they help to defend the colony against disease,” said May.
There’s a bigger takeaway beyond the petri dish. If bees benefit from a rich menu of plant-derived microbes, then a landscape with more kinds of flowers could seed hives with more protective allies. Diversity in the field may translate to resilience in the hive.
None of this means pouring antibiotics into colonies. Instead, the idea is gentler and more targeted: give bees the right roommates.
“In the future, treating bee diseases could be a matter of simply introducing the right beneficial bacteria into hives to help control specific pathogens,” says May.
Journal Reference: Frontiers in Microbiology. DOI: 10.3389/fmicb.2025.1644842
