The Metabolic Characteristics and Microbial Interactions in the Partial Denitrification Systems Fed With Different Carbon Sources

This study systematically investigated the microbial community structure and ecological networks in three partial denitrification (PD) systems driven by sodium acetate (R1), glucose (R2), and glycerol (R3). After 180 days of acclimation, the nitrate to nitrite transformation rates reached 90.15% (R1), 55.47% (R2), and 73.06% (R3). High-throughput sequencing revealed distinct dominant functional microorganisms: Thauera (57.93%) in R1, Azospira (41.63%) in R2, and Saccharibacteria (53.47%) in R3. In R2 and R3, gene functional prediction found that the relative abundance of nitrate reductase (Nar)-related and nitrite reductase (Nir)-related genes was close, but the complex III-related genes gradually decreased, suggesting that nitrite accumulation might correlate with reduced electron transfer efficiency of cytochrome c. In R1 and R2, ecological network analysis demonstrated that Thauera and Azospira exhibited relatively independent ecological subnetworks, whereas Saccharibacteria exhibited extensive interactions with most functional microorganisms in R3. Furthermore, Ohtaekwangia and Anaerolineaceae played crucial roles in maintaining module stability in R2, with Anaerolineaceae additionally acting as module connectors in R3. This study systematically elucidated the metabolic characteristics and microbial interaction mechanisms of PD systems under different carbon sources, providing theoretical support for optimizing PD-anammox coupling technologies.