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Aims <p>Ectomycorrhiza (ECM) sporocarps harbor unique bacteria with high mutual specificity for their fungal host. One such species of bacteria, <i>Paraburkholderia fungorum</i> strain GIB024, isolated from a <i>Rhizopogon roseolus</i> sporocarp in a <i>Pinus thunbergii</i> forest, promotes mycelial growth of <i>R. roseolus</i>. However, the specific interaction between the bacterium and ECM fungi has not been fully investigated.</p> Methods <p>In vitro agar-based plate approaches, including direct and indirect confrontation assays, as well as application of a sterilized bacterial suspension to actively growing ECM strains, were employed. All assays were performed in 1:5 diluted Modified Melin-Norkrans (MMN) medium, with and without glucose.</p> Results <p>We observed that <i>P. fungorum</i> GIB024 significantly promoted the mycelial growth of <i>R. roseolus</i> in an agar medium containing sugar. The bacterium significantly promoted the growth of <i>Suillus bovinus</i> but not that of <i>R. roseolus</i> in a low sugar medium. We then extended the bioassay to a low-sugar medium to focus on <i>Suillus</i> spp. associated with various host plants. <i>P. fungorum</i> GIB024 significantly promoted <i>S. bovinus</i> growth in association with <i>P. thunbergii</i> but not with <i>Pinus densiflora</i>. The bacterium had a neutral or inhibitory effect on the growth of other <i>Suillus</i> spp. associated with <i>P. thunbergii</i> as well as on other <i>Pinaceae</i>. Furthermore, application of a sterilized bacterial suspension produced effects resembling those of a confrontation assay.</p> Conclusions <p>These results suggest that <i>P. fungorum</i> GIB024 is a species-specific fungophile bacterium with mycelial growth-promoting activity targeting ECM fungal strains associated with <i>P. thunbergii</i> (host-plant-dependent specificity).</p>

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Mycelial growth-promotion of bacterium isolated from fruiting bodies of Rhizopogon roseolus and its specificity toward strain of ectomycorrhizal fungi

  • 期刊论文

  • 发表日期：

    2026年7月31日

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  • Toga Pangihotan Napitupulu,
  • Tadanori Aimi,
  • Norihiro Shimomura

摘要

Aims

Ectomycorrhiza (ECM) sporocarps harbor unique bacteria with high mutual specificity for their fungal host. One such species of bacteria, Paraburkholderia fungorum strain GIB024, isolated from a Rhizopogon roseolus sporocarp in a Pinus thunbergii forest, promotes mycelial growth of R. roseolus. However, the specific interaction between the bacterium and ECM fungi has not been fully investigated.

Methods

In vitro agar-based plate approaches, including direct and indirect confrontation assays, as well as application of a sterilized bacterial suspension to actively growing ECM strains, were employed. All assays were performed in 1:5 diluted Modified Melin-Norkrans (MMN) medium, with and without glucose.

Results

We observed that P. fungorum GIB024 significantly promoted the mycelial growth of R. roseolus in an agar medium containing sugar. The bacterium significantly promoted the growth of Suillus bovinus but not that of R. roseolus in a low sugar medium. We then extended the bioassay to a low-sugar medium to focus on Suillus spp. associated with various host plants. P. fungorum GIB024 significantly promoted S. bovinus growth in association with P. thunbergii but not with Pinus densiflora. The bacterium had a neutral or inhibitory effect on the growth of other Suillus spp. associated with P. thunbergii as well as on other Pinaceae. Furthermore, application of a sterilized bacterial suspension produced effects resembling those of a confrontation assay.

Conclusions

These results suggest that P. fungorum GIB024 is a species-specific fungophile bacterium with mycelial growth-promoting activity targeting ECM fungal strains associated with P. thunbergii (host-plant-dependent specificity).