Microbially-driven phosphorus cycling and its coupling mechanisms with nitrogen cycling in mangrove sediments.

The phosphorus (P) cycle plays a crucial role in the biogeochemical cycling of mangrove sediments. However, the diversity of microbially-driven P-cycling and its coupling with nitrogen (N)-cycling remain poorly understood. In this study, we used metagenomic approaches to investigate microbial P-cycling and its potential interactions with N-cycling in mangrove sediments. Our results revealed that pH, total carbon, and total nitrogen were key environmental factors influencing the diversity of P-cycling microbial communities. Phosphorus metabolic pathways differed among mangrove sediment depths. In surface sediments (0-5 cm), microbial communities primarily acquired readily available inorganic phosphorus, whereas, in deeper sediments (>60 cm), they hydrolyzed more persistent triphosphates, reabsorbed nucleotides, and sourced free phosphate, reflecting a shift in phosphorus transport modes. We also identified glutamate metabolism as a potential pathway linking P-cycling with N-cycling, with these functions co-occurring in both contigs and genomes. Additionally, the diversity of microbial communities associated with the P-cycling increased with sediment depth, suggesting that microbially-driven P-cycling diversifies as depth increases. This study provides new insights into P-cycling and its potential coupling with N-cycling through glutamate metabolism, its coupling with N-cycling through glutamate metabolism.