#FEMSmicroBlog: Visualising the soil mycelium


Fungi are enigmatic microorganisms that build intricate underground filaments called mycelia. These thread-like networks play critical roles in nutrient cycling, soil functioning, plant health, and bioremediation. The study “Fungal drops: a novel approach for macro- and microscopic analyses of fungal mycelial growth” in microLife developed a new technique to better understand the development of microbial filaments, as explained by Matteo Buffi, Saskia Bindschedler and Pilar Junier in this #FEMSmicroBlog entry. #FascinatingMicrobes


The mycelium and the fungal network

Filamentous microorganisms grow tube-like structures continuously branching their tips. The resulting mycelial network is highly complex and organised, but without any definite shape. Thanks to their mycelium, fungi are able to explore their environment and exploit resources following rules unclear to the observer.

The fungal mycelium often grows in highly heterogeneous environments such as soil, making its visualisation challenging. The study Fungal drops: a novel approach for macro- and microscopic analyses of fungal mycelial growth” in microLife introduced a new technique to shed light on this fungal network.


Starting from a drop

Replicating the three-dimensional heterogeneity of soil systems in the laboratory is extremely difficult. The “Fungal Drops” method addresses this challenge by creating a controlled and heterogeneous two-dimensional environment.

In this experiment, several small aqueous drops containing nutrients are deposited on a surface suitable for cell adhesion, such as a glass slide or a Petri dish used for cell culture. These nutrient-rich pockets are thus isolated by air-filled gaps.

Into one of these drops, the fungus is added as a spore or as a mycelium fragment. A single fungal spore can grow into a mycelium, but producing spores can be cumbersome. Since mycelium can also re-grow from a fragment, shredded mycelium can be used instead of spores. Disregarding the starting fungal material, the developing mycelium is embedded in nutrient-rich liquid pockets in a configuration similar to the conditions in the soil.

The "Fungal Drops" Method introduced by Buffi et al. (2023).
The “Fungal Drops” Method introduced by Buffi et al. (2023).


Visualising mycelial networks

During the experiment, the fungus grows, exits the drop, and spreads out to explore its surroundings to develop into a mycelial network. This setup is excellent for studying mycelial growth and revealing the remarkable architecture and flexibility of fungal networks.

Using macro- and microscopic analysis, the study showed how mycelial networks adapt in response to changes in environmental conditions.

Mycelial networks also responded to other soil dwellers, like protists, bacteria, or other fungi. Colonization by Fusarium oxysporum, for example, was more effective in co-culture with the bacterium Pseudomonas putida. Yet, the bacterial population collapsed prior to colonization of the drop by Fusarium oxysporum, and the fungus might have used the dead bacterial cells as nutrient sources.

Fungal mycelium visualised by the "Fungal Drops" Method
Fungal mycelium visualised by the “Fungal Drops” Method. From Buffi et al. (2023).

The “Fungal Drops” method is a versatile, easy-to-apply, and low-cost approach to studying filamentous modularity and adaptability. This method offers a unique opportunity to explore the intricate relationships between fungi and other microbes, and thus help better understand their ecological importance. The “Fungal Drops” technique could help develop novel bioremediation strategies and control fungal growth in agriculture and medicine.


About the authors of this blog

Matteo R. Buffi is a Ph.D. student in the laboratory of microbiology at the University of Neuchâtel. For his thesis, Matteo is studying filamentous fungi by developing new methods to observe and quantify behaviours, especially regarding interspecies interactions. Matteo wants to understand the complex interactions that sustain ecosystem functions in forest soils and the means of communication between the biological players found in these ecosystems.

Saskia Bindscheder is a senior lecturer in mycology at the University of Neuchâtel. Her research at the laboratory of microbiology focuses on fungal interactions with both living and mineral components of ecosystems with a focus on biotechnological applications.

Pilar Junier is the head of the laboratory of microbiology at the University of Neuchâtel. She has a background as a microbial ecologist and has a passion for the study of microorganisms in their natural environment. This requires the development of new approaches to study microbial communities in conditions resembling their habitat.

About this blog section

The section #FascinatingMicrobes for the #FEMSmicroBlog explains the science behind a paper and highlights the significance and broader context of a recent finding. One of the main goals is to share the fascinating spectrum of microbes across all fields of microbiology.

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