Fungus-mediated bacterial survival and migration enhance wood lignin degradation.

Bacterial-fungal interactions are increasingly recognized as a key factor in wood decomposition; however, the specific mechanisms underlying these interactions remain unclear. In this study, vanillic acid-utilizing bacteria were isolated from decayed wood colonized by the white-rot fungus Trametes versicolor, and their coexistence and functional impact in a solid wood environment were evaluated. We propose, for the first time, that these bacteria disperse on woody materials with fungal mycelia, survive long-term only in the presence of the fungus, and enhance both wood mass loss and lignin degradation in co-culture. Notably, the co-cultures exhibited lower glucose concentrations and vanillic acid levels released from the rotting wood powder than the fungal monocultures. These results suggest that bacterial glucose and vanillic acid consumption may relieve carbon catabolite repression, thereby promoting the fungal ligninolytic enzyme laccase. This study provides the first experimental evidence that coexisting bacteria can modulate fungal metabolism and wood-decay performance in solid-state systems via both physical and metabolic interactions. IMPORTANCE: White-rot fungi are central to lignin degradation in forest ecosystems; however, the ecological roles of coexisting bacteria in solid wood environments remain poorly understood. Here, we show that the white-rot fungus Trametes versicolor facilitates bacterial migration and long-term survival in wood, enabling bacteria to access fungal-derived aromatic and carbohydrate compounds. Additionally, these bacteria may enhance fungal ligninolytic activity by metabolizing phenolic and sugar intermediates that could otherwise accumulate and affect fungal metabolism. This mutualistic interaction suggests a spatially organized metabolic cooperation that may accelerate wood decomposition. Our findings highlight a novel perspective for bacterial-fungal interactions in structured lignocellulosic substrates and inform microbial strategies for efficient biomass degradation in natural and engineered systems.