Bioactive Sulfide Stimulates Sulfur-Oxidizing and Denitrifying Bacteria to Accelerate Nitrogen Removal: A Novel Biological Approach to Water Purification

Nitrogen pollution causes eutrophication and algal blooms worldwide. Algae-derived organic sulfides can interact with organisms to affect nitrogen cycling, but the associated patterns and mechanisms remain unclear. This study investigated the effects of dimethylsulfoniopropionate (DMSP), an important bioactive sulfide, on nitrogen transformation and removal at the water–sediment interface in microcosm systems (water–sediment and water–sediment–biofilm–benthos). Results showed that DMSP altered the dynamics of total nitrogen and dissolved inorganic nitrogen in overlying water, particularly promoting 74.39% reduction of nitrate in the system containing biofilm and benthos. The presence of DMSP in conjunction with biofilm and bioturbation affected the nitrogen transformation in the sediment. DMSP increased the content of dissolved organic carbon but decreased the content of dissolved oxygen in water. Moreover, it was converted to sulfate in water, enhancing the abundance of bacteria capable of denitrification and sulfur oxidation (such as Pseudomonas) as well as related genes, including narGHI, norBC, soxA, soxC, soxY, and soxZ, in the biofilm. This observation suggests that the process of sulfur oxidation promotes denitrification. The current study highlights the potential applications of DMSP in water purification systems and presents a novel biological approach to aquatic management.