The possible role of trehalose in the mycorrhiza helper bacterium effect

The main objective of the study was to explore the biological pathway that could explain the stimulating effect of mycorrhiza helper bacteria (MHB) on ectomycorrhizal symbiosis. It has been suggested that the ability of MHBs to stimulate mycelial growth is strongly correlated with their effect on ectomycorrhizal establishment; therefore, the role of organic substrates known to be involved in the hyphosphere and mycorrhizosphere effects of this fungal growth promotion were investigated. Therefore, the bacterial influence on fungal growth was tested using two-compartment dishes. One compartment was filled with a minimal medium (M9 medium) amended with different organic compounds (D-glucosamine, oxalic acid, trehalose, malonic acid, citric acid, carboxy-methyl cellulose, starch, or chitin) and inoculated with a MHB isolate (Pseudomonas monteilii strain HR13). The other compartment contained fungal plugs of Pisolithus albus isolate IR100. Fungal radial growth was stimulated only when Pseudomonasamonteilii was grown on M9 medium + trehalose. This result suggests that trehalose has a role in such bacteria-fungus interactions. However, further research, using other biological models, must be undertaken to identify the role of trehalose in the interactions between MHBs and the fungal symbionts at trophic and genetic levels.