Basidiomycete model fungi and their communication in soil

For their life is soil, fungi are well-equipped. The filamentous lifestyle allows them to interact with different soil particles as well as plant roots. The hyphae spanning different niches in soil provide a route by which soil bacteria like Bacillus can access new environments. To delve into such interactions, different molecular signals are produced, among them volatiles. With respect to ectomycorrhizae, the involvement of fungal VOCs in modulating plant response is discussed.

For soil attachment and growth in soil, a model using glass surfaces is presented that also allows to assess thigmotropic clues that lead hyphae to attach to surface veins and into crevices. This goes to show that basidiomycete fungi like Schizophyllum commune can sense surface structures and respond with specific gene expression profiles to different surfaces.

Molecules involved in bacteria-fungi interaction are explored using Bacillus subtilis as a single celled bacterium as well as streptomycetes representing filamentous bacteria in interaction with fungi. Surface interactions of fungi enable bacterial movement, and the inhibition of swarming may indicate that the access of different niches is controlled by the fungus. In interaction with Schizophyllum commune, and in response to structured surfaces, bacterial signaling molecules are shown and the involvement of B pheromone receptor-like proteins, Brls, are discussed.

The specific ectomycorrhizal symbiosis of Tricholoma vaccinum with its compatible host spruce and its low-compatibility host pine is used to show the involvement of volatile terpenoid molecules in host communication. The trees respond with different phytohormone profiles suggesting recognition of beneficial versus pathogenic soil microbes upon terpenes exuded by the fungus in a volatile-only chemical communication setting. Since ectomycorrhizal fungi determine the bacterial microbiome in forest soils, this specific volatile signaling prior to contact between the symbionts is seen as a first row of communication molecules in basidiomycete-host tree symbiosis.