抄録
A recent study revealed that three Bacillus strains isolated from mushroom hyphae stimulated the mycelial growth of ectomycorrhizal (ECM) mushroom strains. In this study, we examined the factors influencing the mycelial growth of ECM mushroom strains using four culture methods: non-contact, bi-plate, spent broth and cell-contact cultures. The relative growth of ECM mushrooms increased when we used the three culture methods (non-contact, bi-plate and spent broth cultures). However, when using cell-contact culture, the bacteria exhibited variable effects, including significant inhibition and stimulation. Significant inhibition of mycelial growth was constantly observed in the co-culture between Bacillus tequilensis MBRr6a and all ECM mushroom strains, ranging from complete inhibition (0.00%) to 67.2%. When B. subtilis MBRr6b and B. pseudomycoides MBSg7b were co-cultured directly with their host mushroom strains, mycelial growth was inhibited, and the relative growth rate was decreased to 76.1% and 56.2%, respectively. When bacterial strains were co-cultured directly with non-host ECM mushrooms, mycelial growth was remarkably stimulated. These results suggest that the key factors influencing the mycelial growth of ECM mushrooms were related not only to water-soluble and volatile metabolites but also to the cell contact with hyphal bacteria. Furthermore, this indicates that the effect was dependent on the bacterial and ECM mushroom strains.
Key words: Ectomycorrhizal mushroom, Hyphal bacteria, Physical contact, Volatile metabolite, Water-soluble metabolite
