Bacterial Diversity and Community Assembly in Deep-Sea Sediments: Observations from the Philippine Sea

Microorganisms are important components of marine ecosystems and are widely distributed across global marine sediments. Although studies on microbial communities in deep-sea sediments have been increasing worldwide, research in the Philippine Sea is still at an early stage. In this study, we investigated the diversity and composition of bacterial communities in deep-sea sediments of the Philippine Sea and their influencing factors. The results revealed that Proteobacteria dominated the sediment bacterial communities, with clear vertical variations in community composition. Notably, bacterial communities in the shallow and deep sediments of the Parece Vela Rift showed marked differences in community composition, including variation in the abundance of taxa previously reported from hydrate- and seep-associated environments (e.g., Aerophobota), suggesting the possible influence of distinct subsurface environmental conditions. Community assembly analyses indicated that stochastic processes predominated across all four sediment cores, with deterministic processes accounting for only 12.3–21.0%, while community composition varied along measured environmental gradients, and sediment Fe showed an apparent association with phylogenetic turnover. These findings provide baseline data for understanding the mechanisms underlying the formation and maintenance of microbial diversity in deep-sea sediments and offer a reference for exploring the ecological functions of deep-sea ecosystems.