Lichens are partnerships between fungi and photosynthetic microorganisms. They are important in microbiology because they show how unrelated organisms can live in close association, and they play significant roles in terrestrial ecosystems.
A lichen is a symbiotic association between a fungus and a photosynthetic partner: either a green alga or a cyanobacterium. Lichens are classified as fungi because of their fungal partner, which belongs to either the Ascomycota or Basidiomycota.
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What is a lichen?
A lichen is a symbiotic association between a fungus and a photosynthetic partner, which is either a green alga or a cyanobacterium.
What are the roles of the fungal and photosynthetic partners in a lichen?
The photosynthetic partner makes photosynthates that the fungus can use. The fungus provides a structure that can help the photosynthetic partner live in drier conditions.
What are the cortex, medulla, and rhizines in a lichen?
The cortex is the tightly packed outer fungal layer, the medulla is the loosely packed inner fungal layer, and rhizines are bundles of fungal hyphae that attach the lichen to a substrate.
How can you distinguish the three major lichen growth forms?
Crustose lichens look crust-like and are tightly attached; foliose lichens have leaf-like lobes; fruticose lichens have rounded structures and a branched appearance.
How can lichens benefit or inform ecosystems?
They help break down rock and contribute to soil formation, some cyanobacteria in lichens fix nitrogen, and lichens can stabilize desert soil. They can also serve as food for caribou and as indicators of pollution.
Quiz questions
Which partners form a lichen?Answer: A fungus and a green alga or cyanobacterium.
What is the body of a lichen called?Answer: The thallus.
What does the fungus generally receive from its photosynthetic partner in a lichen?Answer: Photosynthates made by the partner.
Which lichen growth form is crust-like and tightly attached to its substrate?Answer: Crustose.
How do lichens help contribute to soil production on new lava flows?Answer: They colonize early and help break down rock.
Based on Microbiology by Nina Parker, Mark Schneegurt, Anh-Hue Thi Tu, Philip Lister, Brian M. Forster (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.