Week 9 - Antarctic soil fungi

In 1g of soil in a temperate environment…

there is 3-30km of fungal hyphae and 10^10 bacteria

Saprotrophic microorganisms

Functional group which utilises dead plant material

Includes the majority of decomposers

Ability to penetrate the protective surface of a material and invade at a cellular and molecular level once inside

Rhyzomorph

Long branching structures of mycelia (collection of hyphae)

Importance of mycelium

Translocation of nutrients between microsites and penetration/invasion of detritus (dead material)

Division into nutritional abilities

Zymogenous -> opportunistic species in a dormant condition but capable of rapid growth to exploit readily metabolised resources

Autochtonous -> resident in soil as vegetative populations usually utilising complex polymeric substances

by Winogradsky (1924)

Secondary split based on substrates

Sugar fungi → simple organic compounds used up when available

Celluloytic fungi → break down cellulose

Secondary sugar fungi → secondary products of broken down cellulose

Ligninolytic fungi → lignin

by Garrett (1951, 1963)

Fungal life strategies

r-selected -> short life expectancy, rapidly reproduce using majority of available resources

K-selected -> long life expectancy, small proportion of resources designated to reproduction and any one time, reproduce at the end of the life span

C-selected ->  combative/competitive maximise ability to occupy and exploit resources in conditions of low stress and disturbance

S-selected -> stress tolerant, constantly adapting

Unicellular growth form in bacteria and yeast

Adapted to detritus with high SA:vol

Rapid dispersal

Rapid reproduction

More tolerant of disturbance than mycelia

Small size so colonise pores, cant penetrate harder materials

Success of soil microorganisms

Wide range of substrate utilisation, physiology, reproduction strategies (asexual spores) and genetic diversity

Antarctic soils

2 flowering plants (Colobanthus quitensis and Deschampsia antarctica)

Slow decomposition

High carbon stocks

Rapid regional warming (slowed around 1990-2000, but further increased warming is predicted towards 2100 leading to blooms in vascular plants which would lead to the greening of the arctic, a positive feedback loop contributing to global warming)

Previous study techniques

Culturing techniques, growing microbes from the soil on agar plates isolating pure cultures -> very selective method

Collections of fungal fruit bodies (only certain species produce them, and they often don’t last long)

Lichenized fungi

400 species described in antarctica

Symbiotic partnership of fungi and algae

Non lichenized fungi

1000 species described

Majority ascomycota (68%) them basidiomycota (23%), Zygomycota (5%) and Chytridoimycota (4%)

Current project

Identify fungal communities by sequencing with transects N-S along 3 antarctic islands from subantarctica to maritime antarctica

On each island

1. Record mean annual temperature and precipitation

2. Dig 3 soil pits

3. Take 3 horizontal cores at depth

4. Extract DNA from each sample

5. PCR amplify and sequence DNA using 454 pyrosequencing

Conclusions from hypotheses

Conclusions -> Cox et al (2016)

• Evidence for reduction in species richness moving south

• Smaller proportion of Basidiomycota further south

• Antarctic fungi similar to fungi in other cold places (environmental filtering)