Microbiome change by symbiotic invasion in lichens

Area of Science:

• Symbiotic biology
• Microbial ecology
• Mycology

Background:

• Lichens are symbiotic organisms comprising fungi and algae or cyanobacteria.
• Most lichens form from propagules, but some develop within existing lichens.
• Diploschistes muscorum invades Cladonia symphycarpa, transitioning to an independent thallus.

Purpose of the Study:

• To investigate how symbiotic reorganization impacts lichen-associated microbiomes and photobionts.
• To analyze microbial community shifts during the parasitic-to-independent transition of Diploschistes muscorum.
• To compare photobiont specificity in the invading and host lichens.

Main Methods:

• Sampling of transitional stages of Diploschistes muscorum infecting Cladonia symphycarpa in Sweden and Germany.
• High-throughput 16S rRNA gene sequencing for bacterial community analysis.
• Photobiont-specific ITS rDNA sequencing and fluorescence in situ hybridization (FISH) for photobiont identification.

Main Results:

• A gradual shift in the microbiome was observed during the transition, with retention of some Cladonia-associated bacteria.
• Consistent changes included a decrease in Alphaproteobacteria and an increase in Betaproteobacteria.
• Photobiont specificity differed: Cladonia symphycarpa maintained a consistent photobiont, while Diploschistes muscorum exhibited flexibility.

Conclusions:

• The symbiotic invasion system demonstrates partner reorganization and selection based on functional roles rather than species specificity.
• Lichen development can involve significant shifts in microbial communities and adaptable photobiont associations.
• This highlights the dynamic nature of lichen symbiosis and microbial interactions.