Fungi act as ‘highways’ for bacteria – new tools reveal how microbes travel together on crops

Researchers from Rothamsted Research together with international researchers from University of Neuchâtel, University of Minnesota, Los Alamos National Laboratory and Michigan State University have created innovative 3D‑printed experimental devices that allow them to observe, at scale, how bacteria disperse by travelling along fungal filaments – a phenomenon known as “fungal highways”.

Fungi grow as long thread‑like networks (hyphae and mycelium) that explore their environment. These fungal networks can act as physical bridges across dry or fragmented habitats, enabling bacteria to move into new spaces they could not otherwise reach. Until now, studying these interactions has been technically challenging and hard to scale.

The new study, published in microLife, introduces simple, low‑cost devices that allow researchers to test many bacterial–fungal combinations under different environmental conditions at once. The approach provides a powerful new way to understand how microbial communities form and function in soil and on plants.

“We now have scalable methods to systematically study when, how and why bacteria move along fungal networks,” said Martin Darino, post-doctoral researcher at Rothamsted Research and co‑author of the study. “This helps us understand microbial behaviour in real environments, including fungal infection of plants rather than only under artificial laboratory conditions.”

From soil to crops

Using the new devices, the researchers showed that bacterial movement along fungal highways depends strongly on:

• nutrient availability
• fungal species
• bacterial traits
• how the organisms encounter each other

Under nutrient‑poor conditions, fungi became more exploratory, increasing the likelihood of bacterial transport.

Importantly, the team went beyond laboratory systems and demonstrated fungal‑mediated bacterial transport on wheat plants. The fungus Fusarium graminearum is the major causal agent in the UK and the world of Fusarium Head Blight disease on wheat. The fungus contaminates grain with harmful mycotoxins which makes them not suitable for human and animal consumption. The authors showed that F. graminearum hyphae were able to transport bacteria into neighbouring wheat tissues, suggesting a more intimate interaction, extending beyond co-migration into metabolic cooperation.

“Understanding these interactions matters because fungi and bacteria don’t act alone,” said Kim Hammond-Kosack, who leads the Wheat Pathogenomics team at Rothamsted Research. “These cross-kingdom cooperations are likely to influence fungal disease spread and virulence, microbial competition and ultimately how crops interact with their microbiome.”

Why fungal highways matter

Microbial interactions shape everything from nutrient cycling in soils to plant disease outcomes. Some bacteria that travel with fungi can enhance fungal virulence, while others may suppress disease or help plants tolerate other types of stresses.

The new tools providing a reproducible and adaptable way to study the roles of fungal bridges in a wide range of processes and will help researchers identify:

• which bacteria are most likely to travel with particular fungi
• how environmental stress alters microbial movement
• how microbial partnerships contribute to crop infection or crop protection

The 3-D printed devices are easy to customise and share, allowing laboratories worldwide to adopt the methods and explore fungal highways across agriculture, ecology and biotechnology.

“This opens the door to a more predictive understanding of microbial communities,” said co-author Pilar Junier from the University of Neuchâtel. “Once we understand the rules governing microbial movement, we can begin to manage or exploit these intricate relationships.”

“Microbial interactions play major roles in shaping ecosystems, but they are often difficult to study. By disentangling how microbes interact, we can better understand how microbial communities function,” said co-author Auréline Bouchard from the University of Neuchâtel. “Our 3D-printed device provides a simple and accessible way to study these interactions.”

The researchers say the next steps will involve combining the devices with real-time imaging and molecular tools to track microbes as they move. Ultimately, insights from this research could inform sustainable crop protection strategies and microbiome‑based solutions for agriculture under ever changing environmental conditions.