(WASHINGTON, January 18, 2026) — Researchers have discovered that bacteria naturally found in pollen possess antimicrobial properties that could offer a new defense against threats to both bee and plant health.
A new study published in Frontiers in Microbiology reveals that certain bacteria, specifically endophytic Streptomyces, produce compounds effective against pathogens impacting honeybees and crucial agricultural crops.
- Researchers identified 34 strains of actinobacteria from pollen, with 72% belonging to the Streptomyces genus.
- These bacteria produce compounds that inhibit the growth of pathogens affecting bees, including those responsible for stonebrood and American foulbrood diseases.
- The study suggests that diverse plant life supports a richer microbiome in pollen, bolstering bee health and potentially reducing reliance on chemical treatments.
Honeybee hives store large quantities of pollen, a vital protein source for the colony. However, this pollen is not sterile, harboring a largely unknown bacterial biodiversity that researchers are now finding may play a critical role in bee health. A team from Washington College and the University of Wisconsin-Madison isolated 34 strains of actinobacteria from plant pollen and pollen stored within a hive, according to the study.
Of these strains, 72% were identified as belonging to the Streptomyces genus, known for its ability to produce antimicrobial compounds. Researchers found that the simultaneous presence of these bacteria in flowers, on foraging bees, and within hives suggests regular transfer during foraging, meaning bees collect not only pollen but also the microbes residing there.
Pollen Microbiome Linked to Plant Diversity
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The study indicates a strong link between microbial diversity in pollen and the surrounding plant diversity. A varied flora promotes a richer abundance of beneficial bacteria available to bees, while monocultures may deplete this crucial resource. The composition of the pollen microbiome, previously overlooked, could prove decisive in bolstering colony resilience to diseases.
Natural Compounds Combat Key Pathogens
Researchers assessed the effectiveness of the isolated bacterial strains against six major pathogens – three affecting bees (Aspergillus niger, Paenibacillus larvae, Serratia wilting) and three targeting plants (Erwinia amylovora, Pseudomonas syringae, Ralstonia solanacearum) – using “competition” trials. Virtually all Streptomyces strains tested showed significant inhibition of Aspergillus niger growth, a fungus causing the devastating stonebrood disease in bees, which affects larvae, causing them to harden and resemble stones.
Some strains also demonstrated moderate to strong antimicrobial activity against P. larvae, responsible for American foulbrood, a highly contagious and fatal bacterial disease affecting bee larvae. On the plant side, clear inhibitions were observed against agents responsible for bacterial burns, wilting, and root rot, posing a significant threat to crops like apple trees, tomatoes, and potatoes.
The isolated bacteria produce a diverse range of bioactive metabolites, including PoTeMs (polycyclic macrolactams), surugamides (cyclic peptides), lobophorins (antimicrobial molecules), and siderophores (iron sensors). These compounds are known for their broad spectrum of action, stability, and low toxicity to non-target organisms.
Plant-Bee-Microbe Interactions
Genomic analysis revealed that these Streptomyces are not merely passively transported microbes, but rather plant symbionts, originating from the internal tissues of plants as endophytes. Their presence in pollen indicates they colonize flowers and are then collected by bees during foraging. Genes characteristic of endophytism – including those for plant cell wall degradation, hormone production, and iron capture – were found in all analyzed strains, enabling them to interact with plant tissues.
Once collected, these bacteria are brought back to the hive and continue producing antimicrobial compounds, creating a natural defense mechanism closely linked to foraging behavior. This represents a striking example of a tripartite interaction between plants, microbes, and insects.
A Promising Biological Strategy
Current bee disease treatments largely rely on antibiotics like oxytetracycline and tylosin, but their use is often restricted due to side effects such as altered bee gut microbiota, antibiotic resistance, and potential contamination of hive products. The study notes that Paenibacillus larvae has already developed resistance to oxytetracycline, according to several cited studies.
Given these limitations, introducing beneficial bacteria into hives is gaining traction as a viable alternative. Researchers suggest that inoculating hives with specific Streptomyces strains – isolated from local plants or selected for their antimicrobial effectiveness – via pollen or suitable formulations could strengthen microbial immune defenses without disrupting the ecological balance.
Why It Matters
This research offers a potentially transformative approach to safeguarding both bee populations and agricultural crops. The discovery that naturally occurring bacteria in pollen can combat key pathogens opens the door to more sustainable and targeted biological control methods, reducing reliance on synthetic pesticides and antibiotics. The findings underscore the critical importance of preserving floral diversity to support a healthy pollen microbiome, which, in turn, strengthens the resilience of both pollinators and the food systems they support. This highlights a previously underappreciated connection between plant health, bee health, and overall ecosystem stability.
Source: Claire Reichardt et al., “Endophytic Streptomyces from Honeybee Hives Inhibit Plant and Honeybee Pathogens”. Frontiers in Microbiology (2025).
