Bacillus subtilis is crucial for the normal growth of mycelium for Stropharia rugosoannulata.

In completely sterilized sawdust, Stropharia rugosoannulata mycelium growth is 90%–125% slower than on non-sterilized or incompletely sterilized media, and Bacillus subtilis restores growth.

• Why it matters: Slow or absent growth on fully sterilized substrates limits spawn manufacture for this commercially cultivated mushroom.
• What they did: A promoting strain, T2-19, isolated from substrate colonized by S. rugosoannulata, was identified as Bacillus subtilis by 16S rRNA, ANI, AAI, and dDDH; inoculating B. subtilis on completely sterilized sawdust increased mycelium growth by 8.63%–46.82% depending on bacterial quantity.
• The result: B. subtilis disperses long distances in sawdust using S. rugosoannulata mycelium as a “fungal highway” without microbial contamination symptoms, and it alters cellulase, laccase, and Mn-peroxidase activities, though the mechanism remains unclear.

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