Fungal Forms

Fungal forms are fungi of unknown or multiple affinities, including yeasts, conidial fungi, mycorrhizae, and lichens.

Lichens

Mutualistic relationship between three organisms
- An ascomycete fungus is the heterotroph forming the matrix, absorbing water and minerals
- A unicellular alga or cyanobacterium serves as the autotrophic partner
  - Lichens with cyanobacterium symbiote can fix nitrogen
- (Recently discovered) A unicellular basidiomycete yeast, embedded in the lichen cortex or "skin", that produced chemicals to protect the entire organism
Mostly ascomycetes, ~13,000 spp.
- Polyphyletic group, lichens evolved at least five times
Slow growing: 1-2mm per year
Ecologically important:
- pioneer species on rocks, barren soils as well as bark
- extremely widespread (arctic to tropics, wet to dry)
- great indicators of air pollution since they are sensitive to sulfur and nitrogen
Forms: crustose, foliose, fruticose
Lichens may date back to the Proterozoic, but the earliest direct evidence is Spongiophyton from the Early Devonian

Yeasts

Unicellular fungi belonging to Ascomycota, Basidiomycota, or Mucoromycota
Reproduce through budding (asexual)
- Rarely conduct sexual reproduction
Commercially used as a source of ethanol or CO2
- Crucial in the production of wine, beer, and bread
Recently discovered basidiomycete yeasts serve as a 3rd partner in lichens (see lichens - below)

Above: Magnified image of yeast cells

Conidial Fungi

Artificial assemblage of asexual fungi (15,000 spp.)
Once called Deuteromycetes or “Imperfect” Fungi
Reproduce asexually through conidia (asexual spores)
Mostly ascomycetes, some basidiomycetes, and mucoromycetes
Include Athlete's Foot and Penicillium

Above: Conidia of Penicillium

Mycorrhizae

A mutualistic relationship between plant roots and a fungus
- Plants provide the products of photosynthesis (carbohydrates)
- Fungi provide water and minerals
- Few roots hairs grow on plant roots since the fungus is much more efficient at absorbing water and minerals
More than 90% of all plant families examined have this relationship
- 75% of all seed plants are assumed to have mycorrhizae
There are two types of mycorrhizae: endomycorrhizae and ectomycorrhizae

Endomycorrhizae

Fungi invade the root cells
Also called vascular-arbuscular mycorrhizae (VAM)
These are usually glomeromycete
In nature, these are more common than ectomycorrhizae

Ectomycorrhizae

These fungi surround the plant root as a fungal sheath
They produce special hyphae called haustoria which penetrate root cells
These fungi tend to be basidiomycetes, but sometimes ascomycetes
Sometimes these fungi will produce "fairy rings" of basidioma around the tree in which they colonize

Above: macroscopic example of ectomycorrhizae on roots

Above: Ectomycorrhizae of Amanita on a Larix root

Additional Resources

Urban lichens as an emerging model for urban evolution (Evankow et al., 2025)
Fungal allies arm plant roots against disease by rewriting the rules of infection (Phys.org 11Dec2025)

└Mutualist-pathogen co-colonization modulates phosphoinositide signatures at host intracellular interfaces (Guyon et al., 2025)

When indoor plants go overboard: Too much greenery can raise stress levels (Phys.org 4Nov2025)

└How much nature do we need? An exploration of dose-response relationships between indoor nature dose and building occupant well-being (Bianchi & Billington, 2025)

Lichens and drones reveal dinosaur bones (Phys.org 3Nov2025)

└Remote sensing of lichens with drones for detecting dinosaur bones (Pickles et al., 2025)

'Plant-mycorrhiza synergy' can revitalize forest restoration (Phys.org 15Aug2025)

└Li et al. (2025) Mycorrhizal allies: synergizing forest carbon and multifunctional restoration

Mediterranean bacteria may harbor new mosquito solution (Phys.org 7Jul2025)

└Wood et al. (2025) Bacteria isolated from biodiverse Mediterranean island habitats yield a large array of biopesticidal metabolites against mosquito larvae

Most plant-friendly fungi are a mystery to scientists (The Conversation 5Jul2025)

└van Galen et al. (2025) The biogeography and conservation of Earth's 'dark' ectomycorrhizal fungi,

Coveted red dye may owe its origins to a hidden fungal partner in lac insects (Phys.org 17Jun2025)

└Vaishally et al. (2025) An endosymbiotic origin of the crimson pigment from the lac insect

Yeast Converts Human Urine Into Valuable Bone Material (ScienceBlog 17Jun2025)

└Muller et al. (2025) Cost-effective urine recycling enabled by a synthetic osteoyeast platform for production of hydroxyapatite

Mysterious fungi: Researchers pinpoint hotspots of 'dark taxa' across Earth's underground ecosystems (Phys.org 10Jun2025)

└van Galen et al. (2025) The biogeography and conservation of Earth’s ‘dark’ ectomycorrhizal fungi

Africa has the highest rate of forest loss in the world—what the G20 can do about it (The Conversation, 4Jun2025)
Bacteria hitch a ride on yeast puddles to zoom around (Phys.org, 4Jun2025)

└Badal et al. (2025) Dynamic fluid layer around immotile yeast colonies mediates the spread of bacteria

Yeast reveals how species adapt to a warmer climate (Phys.org, 21May2025)

└Molinet & Stelkens (2025) The evolution of thermal performance curves in response to rising temperatures across the model genus yeast

How lichens are bringing stone to life and reconnecting us with the natural world (The Conversation, 19May2025)
Lichens could survive on Mars (Phys.org, 8Apr2025)

└Skubala et al. (2025) Ionizing radiation resilience: how metabolically active lichens endure exposure to the simulated Mars atmosphere

Inoculating soil with mycorrhizal fungi can increase plant yield by up to 40% (Phys.org, 29Nov2023)

└Lutz et al. 2023. Soil microbiome indicators can predict crop growth response to large-scale inoculation with arbuscular mycorrhizal fungi

Mycorrhizae may help store more than a third of fossil fuel emissions (ZME Science, 6Jun2023)

└Hawkins et al. 2023. Mycorrhizal mycelium as a global carbon pool

Are Trees Talking Underground? For Scientists, It's In Dispute (NY Times 7Nov2022)
The Idea That Trees Talk to Cooperate Is Misleading (SciAm 19Jul2021)
Lichens are a symbiosis of three (not two) partners (Science 2016)
Plants force fungal partners to behave fairly (University of Zurich 2016)
Researchers evolve a multicellular yeast in the lab in 2 months (Ratcliff et al., 2011)
Mycorrhizae may not be mutually beneficial (IIASA, 2014)
On Fungi and Forest Diversity (In Defense of Plants, 2017)
Coevolution of roots and mycorrhizae (Brundrett, 2002)

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