Effects of Perfluorobutanesulfonic acid (PFBS) on the sediment microbial communities, and the interaction mechanism with urease and extracellular polymeric substances (EPS)

The influence of perfluorobutane sulphonic acid (PFBS) on sediment microbial communities and nitrogen cycling was systematically investigated in this study. After 28 d of PFBS, the diversity of sediment microorganisms was inhibited, with rare bacterial community demonstrating stronger structural decisive role than abundant taxa. Meanwhile, PFBS induced the secretion of extracellular polymeric substances (EPS), causing elevated reactive oxygen species levels and triggering antioxidant defences. EPS could also act as a barrier between PFBS and urease to reduce the toxicity of PFBS to urease. In the PFBS-urease-EPS system, ultraviolet-visible spectroscopy revealed intensified absorption peaks corresponding to π→π* transitions in peptide backbone structures, indicating that there was an interaction between urease and EPS, a change in the structure of the urease backbone. And the increase in α-helix content indicated that the secondary structure of urease becomes more compact and improves urease activity, which subsequently facilitated ammonium nitrogen (NH₄⁺-N) production in sediments. Partial Least Squares Path Models (PLS-PM) indicated that PFBS stress directly altered the abundance of nitrogen-cycling bacteria, upregulated genes encoding enzymes, and increased the activities of key enzymes of nitrogen-cycling processes, thereby promoting nitrogen cycling.