Researchers discover that pollen gathered by honeybees contains antimicrobial-producing bacteria, offering a potential eco-friendly solution to protect bee colonies from infections
A groundbreaking study reveals that pollen collected by honeybees harbours antimicrobial-producing bacteria capable of defending hives against various pathogens.
The research, led by Dr Daniel May from Washington College, identified strains of Streptomyces, a genus known for its antibiotic properties, both in plant pollen and within honeybee hives. These findings suggest that bees inadvertently transport beneficial bacteria back to their colonies, enhancing hive resilience against diseases.
“We found that the same beneficial bacteria occur in pollen stores of honeybee colonies and on pollen of nearby plants,” said Dr Daniel May, a faculty member at Washington College in Maryland, US, and the corresponding author of a study in Frontiers in Microbiology.
“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.”
Streptomyces bacteria from flowers and pollen help protect honeybee hives from harmful pathogens
The researchers analyzed the Phylum Actinobacteria, the source of two-thirds of the antibiotics currently in clinical use. Between April and June 2021, they collected pollen from ten native plant species at the Lakeshore Nature Preserve, located at the University of Wisconsin-Madison. They also collected pollen from the hives of a nearby honeybee.
The team isolated 16 strains of actinobacteria from plants, and 18 strains from pollen stores inside the hive. DNA barcoding and genome sequencing revealed that the same or closely related species occurred in both types of samples. They found that 72% belonged to the genus Streptomyces, the source of many compounds used in medicine and agriculture, for example, as antibiotics and antiparasitic drugs.
They conducted ‘competition assays’, where they grew pathogens with Streptomyces. Nearly all of these proved to be effective inhibitors of the mould Aspergillus niger, which can cause a honeybee disease called stonebrood. Individual strains also proved moderately to intensely active against two bacterial pathogens of honeybees, Paenibacillus larvae and Serratia marcescens, as well as against three pathogens of crops: Erwinia amylovora, Pseudomonas syringae, and Ralstonia solanacearum.
“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.
The future of managing bee diseases
The researchers found definitive genomic evidence that the sequenced species are true endophytes, rather than merely associating loosely with plants. Their genomes contain genes for enzymes that enable Streptomyces to colonize plant tissues, produce growth-promoting hormones for their hosts, and scavenge metals in the root environment.
The findings highlight that endophytes still harbor a wide range of bioactive compounds, many of which could play a crucial role in supporting honeybee health. They also indicate that habitats with diverse plant species benefit bees by providing access to a broader variety of actinobacterial endophytes.
“Looking ahead, managing bee diseases might one day involve simply introducing the right beneficial bacteria into hives to target specific pathogens,” concluded May.