Truffle Microbiome Is Driven by Fruit Body Compartmentalization Rather than Soils Conditioned by Different Host Trees

Area of Science:

• Mycology and Microbial Ecology
• Plant-Fungal Interactions
• Soil Science

Background:

• Truffles are economically valuable ectomycorrhizal fungi forming symbiotic relationships with host trees.
• The truffle's life cycle is intertwined with its associated microbiome, but drivers of this microbiome are unclear.
• Understanding truffle microbiome composition is crucial for truffle cultivation and ecological studies.

Purpose of the Study:

• To identify and compare fungal and bacterial communities within different truffle compartments (bulk soil, adhering soil, peridium, gleba) of *Tuber indicum*.
• To determine whether truffle compartments or host trees are the primary drivers of the truffle microbiome.
• To analyze the core microbiome and microbial ecological networks associated with truffles.

Main Methods:

• High-throughput sequencing of ITS (fungal) and 16S (bacterial) ribosomal DNA from four truffle compartments.
• Bioinformatic analysis to characterize fungal and bacterial communities.
• Microbial ecological network analysis to assess community interactions and identify keystone species.

Main Results:

• Truffle microbiome composition was predominantly influenced by associated compartments, not host trees.
• Bacterial communities dominated the truffle microbiome and exhibited more complex interacting networks than fungal communities.
• Distinct shifts in core fungal (Basidiomycota to Rozellomycota) and bacterial (Bacteroidetes to Proteobacteria) communities were observed from soil to truffle tissues.

Conclusions:

• Truffle compartments, particularly the gleba, exert strong niche-based selection on the associated microbiome.
• Microbial interactions are more positive within truffle tissues compared to surrounding soil, with specific bacterial genera acting as keystone hubs.
• This study reveals the complex dynamics and compartment-specific drivers of truffle microbiome assembly and function.