Abstract
The large-scale application of algae-bacteria systems in wastewater treatment faces two key challenges: inefficient post-cultivation separation and insufficient understanding of their cross-kingdom interactions. To address these limitations, we developed a dialysis membrane photobioreactor (DMP) that simultaneously enables effective microalgae-bacteria separation and mechanistic investigation of their interactions. The DMP system, integrating microalgae-activated sludge consortia, achieved significantly higher removal efficiencies for nitrogen (95.8 %), phosphorus (68.1 %), and chemical oxygen demand (96.1 %) compared to conventional activated sludge, while also enhancing microalgal biomass production. Mechanistic studies revealed that microalgae promoted the synthesis of cross-kingdom signaling molecules (C6-HSL and IAA), establishing a molecular dialogue between algae and bacteria. Multi-omics analyses uncovered bidirectional regulation: microalgae reshaped bacterial community structure and upregulated bacterial IAA synthesis genes, while bacteria reciprocally activated microalgal IAA-related genes. This mutual feedback mechanism amplified cross-kingdom signaling and synergistically upregulated functional genes involved in nitrogen/phosphorus metabolism, driving enhanced pollutant removal. Our findings demonstrate that the DMP system fosters a syntrophic partnership where AHLs and IAA mediate bidirectional metabolic regulation-simultaneously optimizing pollutant degradation and biomass conversion. This work provides both fundamental insights into algae-bacteria communication and a practical framework for advancing wastewater bioremediation technologies.
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