Cyclic di-GMP triggers filamentous blooms and their mitigation via phosphodiesterases

Filamentous blooms pose substantial threats to aquatic ecosystems, human health, and economies. In wastewater treatment plants, the frequent occurrence of filamentous blooms results in marked reductions in treatment efficiency and the deterioration of effluent quality. However, effective strategies for the rapid suppression of filamentous bacterial proliferation remain inadequately explored. In this study, intracellular cyclic diguanylate monophosphate (c-di-GMP) signaling was found to mediate filamentous bloom behavior in response to extracellular environmental deterioration. During bloom conditions, filament length reached 0.85 μm/μm² and sludge volume index (SVI) increased to 450 mL/g, while intracellular c-di-GMP levels exceeded a threshold of 20 μg/g suspended solids (SS). Concurrently, the expression of c-di-GMP synthetases was upregulated (1.03-4.88-fold), whereas the expression of phosphodiesterases (PDEs), which mediate c-di-GMP degradation, was downregulated (-10.53 to -38.98-fold). These changes were associated with the sequential activation of cell cycle processes and physiological metabolic pathways, ultimately promoting the proliferation of filamentous bacteria. To counteract this process, PDE-loaded chitosan/alginate materials were developed to disrupt c-di-GMP signaling and suppress filamentous blooms. This approach enabled rapid system recovery, reducing filament levels to 0 μm/μm² and SVI to 84 mL/g within 48 h. These findings enhance current understanding of c-di-GMP signal transduction under adverse environmental conditions and offer novel insights into the development of rapid-response strategies to mitigate filamentous bloom events in aquatic ecosystems.