ABSTRACT

Wood-fall micro-ecosystems contribute to biogeochemical processes in the oligotrophic deep ocean. However, the community assembly processes and biogeochemical functions of microbiomes in wood fall remain unclear. This study investigated the diversity, community structure, assembly processes, and functional profilesprofilesof bacteria and fungi in a deep-sea wood fall from the South China Sea using physicochemical indices, amplicon sequencing, and metagenomics. The results showed that distinct wood-fall contact surfaces exhibit habitat heterogeneity. The bacterial community of all contact surfaces and the fungal community of seawater contact surface (SWCS) were affectedaffectedaffectedby homogeneous selection. In SWCS and transition region (TR), bacterial communities were influencedinfluencedby dispersal limitation, whereas fungal communities were affectedaffectedaffectedby homogenizing dispersal. The Venn diagram visualization revealed that the shared fungal community between SWCS and TR was dominated byAspergillaceae. Additionally, the bacterial community demonstrated a higher genetic potential for sulfur, nitrogen, and methane metabolism than fungi. The sediment contact surface enriched modules were associated with dissimilatory sulfate reduction and methanogenesis, whereas the modules related to nitrate reduction exhibited enrichment characteristics in TR. Moreover, fungi showed a stronger potential forlignocellulaseproduction compared to bacteria, withMicroascaceaeandNectriaceaeidentifiedidentifiedas potential contributors to lignocellulose degradation. These results indicate that environmental filteringfilteringfilteringand organism exchange levels regulated the microbial community assembly of wood fall. The biogeochemical cycling of sulfur, nitrogen, and methane was mainly driven by the bacterial community. Nevertheless, the terrestrial fungiMicroascaceaeandNectriaceaemight degrade lignocellulose via the combined action of multiplelignocellulases.