A microbial consortium for mariculture wastewater Treatment: Metabolic reprogramming ensures enhanced nitrogen and...

Excessive inputs of nitrogen (N) and phosphorus (P) from mariculture significantly exacerbate coastal eutrophication. However, fluctuating nutrient compositions and high salinity often compromise the efficacy of conventional biological treatment. In this study, we developed a defined, environmentally safe microbial consortium (Sp-2507) comprising seven compatible marine sponge isolates. Sp-2507 demonstrated efficient and stable nutrient removal compared to individual strains, achieving 95% inorganic nitrogen removal, 98% phosphorus removal, and complete Chemical Oxygen Demand (COD) degradation within 48 h. Crucially, the consortium circumvented the inherent limitations of monocultures, such as incomplete denitrification or nitrite accumulation, maintaining functional robustness across ammonium-(NH₄⁺), nitrate-(NO₃^-), and mixed-nitrogen regimes. Metatranscriptomics and RT-qPCR revealed that this functional resilience was underpinned by nitrogen-source-driven metabolic reprogramming. Ammonium availability prioritized assimilatory pathways (GS-GOGAT) and polyphosphate synthesis; conversely, nitrate triggered the full denitrification cascade (narG-nirS-norB-nosZ). Under mixed-nutrient conditions, the consortium exhibited simultaneous activation of both assimilatory and dissimilatory processes. This adaptability was further attributed to niche partitioning and division of labor: the abundance-driven generalist Alteromonas species sustained core metabolic flux, while activity-driven specialists Marinobacter served as the primary denitrifier, and Tritonibacter provided essential nirK-mediated nitrite reduction. These findings elucidate how metabolic plasticity and interspecies coordination enable efficient nutrient remediation, providing a framework for rationally designing synthetic microbial communities in environmental biotechnology and guiding future applications in complex mariculture environments.