Experiment 20 - Microbial Symbiosis In The Lichen

What is lichen?

An association of an alga or cyanobacterium with a fungus

With what conditions can lichens grow under?

At low temperatures and predominate in extreme environments, essentially in substrates that are usually unsuitable for the growth of other plants

What is the lichen thallus made up of?

Tightly woven fungal mycelia

What is below fungal mycelia?

Algal cells

What is below algal cells?

Another layer of fungus

How does the bottom layer potentially attacth to the substrate?

By short twisted strands of hyphae called rhizomes/rhizoids

What is the fungal partner of mycobiont a member of?

Ascomycetes

What is the algal component of phycobiont?

Green algae of the genera Trentepholia or Trebouxiia

What if the phycobiont is a member of cyanobacteria?

They may be capable of nitrogen fixation

Where else can the algae in lichen be found?

In the free-living state

What is mutualism?

Where both partners derive a benefit from the symbiotic relationship

Why are lichens an example of mutualism?

Because algal components are photosynthetic so they metabolize CO2 and H2O to produce organic materials which are available to the mycobont

What does green algae and cyanobacteria produce?

Sugar alcohol and glucose

How are carbon compounds used?

They are converted to other sugar alcohoks and used as an energy source.

What does the fungal component provide?

Mechanical support and protection of the alga, and some inorganic nutrients required by the alga.

What is one of the most important benefits to the alga?

A microenvironment high in water

What happens to the water in the microenvironment?

It is absorbed and stored by the fungus