Tripartite interaction between wood-decay Basidiomycetes andhabitat sharing microbes

Wood-decay basidiomycetes, such as the ubiquitous white-rot fungus Schizophyl-
lum commune, fulfill an important ecological role by contributing to global carbon
cycling through the degradation of lignocellulose and woody material. However,
the brown-rot fungus Serpula lacrymans also represents an economic burden, by in-
vading buildings and destroying wood construction material. Natural environments
of both fungi are characterized by the interaction with habitat sharing microor-
ganisms. Besides competition with other fungal decomposers, both fungi interact
with bacteria. Such bacterial-fungal interactions can be classified as mutualistic or
antagonistic, with levels in between, and often involve the production of natural
products. While Bacillus subtilis attaches to the hyphae of S. commune (fungal
highway), it induces the production of natural products including terpenoids in S.
lacrymans.

The aim of our study is to understand how consortia stimuli are recognized and
transduced inside basidiomycete cells. Special attention is given to elucidate the
production of terpenoids in S. commune and how they mediate microbial inter-
actions. We use knockout and overexpression of genes in signaling cascades of
S. commune to identify pathways involved in the interaction between both fungi.
Growth and combative ability are evaluated on defined media with different carbon
sources associated with wood and stressors of signaling pathways. Changes in
gene expression due to bacterial cues are anaylzed by RT-qPCR. Furthermore, we
characterize the inter- and intra-kingdom interactions by micromorphology and flu-
orescence microscopy. Putative terpene synthases of S. commune are characterized
by heterologous expression.

Overall, our results help to elucidate the dynamic interactions between fungi and
bacteria and highlight the importance of terpenoids as predominant natural product
of basidiomycetes.