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.