Lichens Flashcards
Which pathways are we certain that symbionts do NOT make contact with in lichens?
CSSP and MiSSP7
What is the narrative surrounding lichens?
A fungus co-occurs with one or more algae/cyanobacteria
The alga provides sugars for use by the fungus
The fungus provides a regulated environment that optimizes algal growth
What do real lichens look like?
Biophysical properties: dry = some brittle, some flexible; moist = specific torsion. elasticity, flexibility
Shape: flat, round
Water relations: ability to take up or get rid of water
Where are yeasts in lichen typically found?
In the polysaccharide layer that coats the lichen
Letharia lichens consistently contain which 3 fungi?
Hyphal ascomycete
Two basidiomycete yeasts
How have the overlooked fungi been missed?
Primer bias
Insufficient sequencing coverage
What is primer bias?
Primers are made with a priori knowledge
Can’t make a primer for something you cannot see or do not know exists
What are fungi cemented together by in lichens?
An extracellular polysaccharide layer
What is the EPS made of?
Ascomycetes: maybe galactomannans
Basidiomycetes: maybe GXM exo-polysaccharides
What are the visual points of reference for polysaccharides?
Lectin-based localization
Direct analysis of monosaccharide profiles
What are the GXM motifs?
Mannose
Glucuronic acid
Xylose
Fucose
Which fungi produce GXM?
Tremellaceae like snow fungus
What breaks down GXM in nature
Lichens have what?
Numerous high-frequency symbionts that easily escape detection
What is the most common lichen symbiont worldwide?
Acetobacteraceae tie with or surpass Trebouxiaceae algae as the most common
How many bacterial families are on par with algae in frequency?
4
What is the frequency of Cystobasidiomycetes?
They are found in at least 1/3 of Tremellomycetes and 2/3 of lichen metagenomes
Cyanobacteria sugar assimilation?
Glucose assimilates into mannitol and arabitol
Trentepohlia sugar assimilation?
Erythritol assimilates into erythritol
Trebouziophyceae sugar assimilation?
Ribitol assimilates into mannitol and arabitol
What are some early lichen goods exchange observations?
Lichens lose considerable amounts of polyols during wetting-drying cycles
Much of the cellular carbon uptake in the fungus is kept in a soluble fraction
Most lichens do not grow much
Why are lichens not great lab models?
They grow extremely slow
What mutualism arose from gene loss?
Saprotrophs evolved into mycorrhiza
Almost all orphan lineages of lichens descend from what?
A common ancestor
The members of the orphan lineage clade have what?
Some of the smallest degradative CAZyme arsenals in Ascomycota
Lichen fungal symbionts from the Dothideomycetes have what?
Some of the largest degradative CAZyme arsenals
Does symbiosis with an alga predict CAZyme and transporter arsenal size?
No, there is a range
When should lichen have a genomic signal for PCWDEs?
If lichen fungi are getting carbon from other sources, fungal symbionts from lichens with strong organic substrate preferences should have this
Why are non-reducing sugars Janus carbohydrates?
They have two uses: growth/respiration and protection
What is the support for nutritional symbiosis?
CO2 exchange and CHla content are correlated in whole lichens
Chla content and relative growth rate are correlated in whole lichens
What do mycorrhizal genomes exhibit following glucose subsidy?
Loss of CAZymes
What do lichen fungi exhibit a greater range of than ectomycorrhizae?
CAZyme arsenals
CAZyme arsenal size varies with what?
The type of photobiont export
What is the future direction for lichen research?
Does the duel function of polyols drive the evolution of slow growth?
If the polyol pool is needed for survival, there would be costs that use this pool for growth
