Bacterial communities in the cultivated wood logs of Grifola frondosa

A Japanese popular Grifola frondosa (maitake) cultivation method called wood log cultivation includes two steps, mycelium grows around wood log in a plastic bag, and then transfer mycelium spread wood log into casing substrates in the forest. This kind of method still popular in Japan due to its low cost and high-quality crops production. Recently, the importance of microbiome which inhabited in mushroom cultivation surrounding has been emphasis; however, no study has been reported on the microbial communities in maitake cultivation. This study aimed to elucidate how the bacterial communities changed in wood logs and its interaction with maitake during maitake cultivation. Due to biomass of maitake was observed in wood logs, but not found in casing sand, we investigated the bacterial communities in wood log samples. From the results, phyla Proteobacteria, Firmicutes, and Gemmatimonadota play key roles in changes of microbiome composition. In functional profile, bacteria communities of maitake cultivated wood log samples showed higher relative abundance in cellulolysis, glycolysis, TCA cycle and many biosynthesis pathways compared to the control samples (without inoculation). These results suggested that the bacterial communities inhabited in maitake cultivated wood logs may help maitake to degrade wood cellulose, and part of glucose from cellulose degraded by both maitake and bacteria was used for bacterial TCA cycle instead of fermentation. Additionally, bacteria may also produce some chemicals that maitake mycelium need. On the other hand, different cultivation stage showed different network structure. Class Gammaproteobacteria was considered a potential keystone taxon for microbiome network stability of maitake cultivated wood logs by network analysis. These results will be helpful to understand microbiome in maitake cultivated surrounding and improve maitake wood log cultivation.