Mycelium

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What is mycelium?


Mycelium are the branching roots of fungi. They intertwine and form the most voluminous previously known living organism.  The mechanical strength of mycelium comes from its cell wall structure, which is made out of components like chitin beta-glucans and proteins like mannoproteins and hydrophobins (Haneef et al., 2017). These cell wall components strengthen when exposed to high temperatures, creating a rigid and durable material.

Structure of fungal mycelium. The random branching of the mycelium hyphae creates dense fibrous networks. Each fungal cell is separated by crossing septa, and encapsulated by a cell wall of layering structural proteins (Adapted from Haneef et al., 2017). 

A biological building material


Mycelium properties as a possible building material are currently explored and commercialized by companies like Ecovative and MycoWorks, who have developed standardized procedures to grow fungi with specific characteristics for different applications. Our project stands humbly on the shoulders of these giants.

Mycelium is impressive in its sustainability. It generates no carbon footprint during its production since it feeds on organic matter, such as food waste.Mycelium is completely biodegradable, and can grow into almost any shape as long as there is a mould to direct its growth.

Further, mycelium bricks are so light that they can float on water, and so durable that they withstand substantial pressures without fracturing (Islam et al.,2017). Finally, mycelium can be grown on location, minimising any environmental costs of transportation.

Material tunability


The excitement around mycelium based materials evolves from its tunability. Simply changing the growth conditions, like changing nutritional source, can increase mycelium’s morphology and possibly strength (Haneef et al., 2017). Furthermore, mycelium growth has been show to increase under magnetic fields (Jamil et al., 2012). This adaptability opens wide possibility to manipulating mycelium by changing environmental factors, as well as emerging targeted genome editing such as CRISPR/Cas9 genome editing (Deng et al., 2017).

CRISPR/Cas9 genome editing through knockin, deletion or transcriptional modifications could be used to engineer desired properties to mycelium strains used for biomaterials.

References


Deng, H., Gao, R., Liao, X. and Cai, Y. (2017). CRISPR system in filamentous fungi: Current achievements and future directions. Gene, 627, pp.212-221.

Haneef, M., Ceseracciu, L., Canale, C., Bayer, I., Heredia-Guerrero, J., & Athanassiou, A. (2017). Advanced Materials From Fungal Mycelium: Fabrication and Tuning of Physical Properties. Scientific Reports7, 41292. doi:10.1038/srep41292

Islam, M. R., Tudryn, G., Bucinell, R., Schadler, L., & Picu, R. C. (2017). Morphology and mechanics of fungal mycelium. Scientific Reports, 7, 13070. 

Jamil, Y., Haq, Z., Iqbal, M., Perveen, T. and Amin, N. (2012). Enhancement in growth and yield of mushroom using magnetic field treatment. International Agrophysics, 26(4).

Creating fungal-bacterial symbioses

A beautiful friendship


Engineering relationships between microbes and mycelium could enhance existing biological properties of fungi. Bacteria and fungi are known to naturally interact through physical association as well as molecular communication (Frey-Klett et al., 2011). Previous studies have shown existing endosymbiotic relationships between e.g. photosynthetic cyanobacteria and mycelium hyphae, which provide protection, water and nutrients to the bacteria, resulting in improved atmospheric acetylene reduction and nitrogen fixation (Lumini et al., 2006). In exchange, the bacteria supply carbon and nitrogen to the mycelium to improve its growth.

Symbiosis between mycelium fungal hyphae and endosymbiotic cyanobacteria. Photosynthetic Nostoc cyanobacteria become encapsulated within the fungal cell membrane, where they supply fixed nitrogen and carbon to the host (Frey-Klett et al., 2011).

 

Useful interactions


Other bacterial strains such as Pseudomonas fluorescens have shown to increase mycelium biomass in unfavourable conditions (Frey-Klett et al., 2011). Further, proteomic and lipid metabolite profiling of Gigaspora margarita fungus grown with Candidatus bacteria show changes in the protein and lipid content of mycelium cell walls (Salvioli et al., 2010). The relationship also increases fungal bioenergetic ATP production, sporulation and responsiveness to branching inducing molecular signals (Salvioli et al., 2015). Additionally, mixed bacterial-fungal consortia have been shown to biodegrade fungal hydrocarbons, such as self-inhibitory metabolic factors that could promote the fungal growth (Frey-Klett et al., 2011). The symbiotic relationships show evidence of inheritable genetic changes within both bacterial and fungal genomes, opening a chance for directed evolution.

Possible effects of synthetic mycelium-bacterial symbiotic relationships.

A synthetic symbiosis between specific endosymbiotic bacteria and mycelium could therefore be used to perpetuate the growth and structural endurance of fungal hyphae on the cellular level. Mycelium can support bacterial species germination and survival in culture conditions through water and nutrient exchange (Worrich et al., 2017). The same method could be used to create an optimised synthetic bacterial-fungal consortia during laboratory mycelium culturing. The strategy could also help identify key nutritional metabolites for designing external supplements to maximise mycelium development.

Sources


Frey-Klett, P. et al. (2011). Bacterial-Fungal Interactions: Hyphens between Agricultural, Clinical, Environmental, and Food Microbiologists. Microbiology and Molecular Biology Reviews, 75(4), pp.583-609.

Lumini, E. et al. (2006). Endobacteria or bacterial endosymbionts? To be or not to be. New Phytologist, 170(2), pp.205-208.

Salvioli, A., et al. (2010). Endobacteria affect the metabolic profile of their host Gigaspora margarita, an arbuscular mycorrhizal fungus. Environ. Microbiol. 12:2083–2095.

Salvioli, A. et al. (2015). Symbiosis with an endobacterium increases the fitness of a mycorrhizal fungus, raising its bioenergetic potential. The ISME Journal, 10(1), 130-144. 

Worrich, A. et al. (2017). Mycelium-mediated transfer of water and nutrients stimulates bacterial activity in dry and oligotrophic environments. Nature Communications, 8, p.15472.