Mycelial Symbiotic Bacterial Communities and Their Associations with Mycelial Traits in Cultivated Edible Mushrooms

Edible mushroom mycelia harbor diverse mycelium symbiotic bacterial communities (MSBCs), yet the extent to which these communities vary among mushroom strains and relate to mycelial physiological traits remains poorly understood. Here, eight edible mushroom strains representing six species were investigated to characterize MSBC composition and explore its potential associations with mycelial growth, nutrient composition, and extracellular oxidative enzyme activities. Using 16 S rRNA gene amplicon sequencing, we revealed that bacterial alpha diversity was largely conserved among strains, with no significant differences detected in Shannon and Simpson indices. However, principal component analysis showed partial separation among bacterial communities, and PERMANOVA confirmed significant differences in overall MSBC structures among strains (R² = 0.422, p = 0.001). Across all strains, Firmicutes, Proteobacteria, Actinobacteria, and Bacteroidetes represented the dominant bacterial phyla. Several prevalent genera, including Tepidimicrobium , Acinetobacter , Enterobacter , Lactobacillus , and Sphingomonas , exhibited distinct abundance distributions among strains, while LEfSe analysis identified strain-discriminative bacterial taxa. Comparisons within species revealed that closely related strains of Flammulina filiformis and Hypsizygus marmoreus maintained similar alpha diversity but displayed differentiated bacterial community compositions. Redundancy analysis and Spearman correlation analysis further revealed significant associations between specific bacterial taxa and mycelial growth, nutrient composition, and extracellular oxidative enzyme activities. Collectively, these findings demonstrate that MSBCs consist of conserved dominant bacterial lineages alongside strain-dependent community variation, and highlight potential links between symbiotic bacterial assemblages and mycelial physiological characteristics in edible mushrooms.