Marine-derived Pseudomonas sp. H1R1 with HN-AD capacity: Construction of algae-bacteria symbiotic system for enhanced carbon-nitrogen metabolism

The strain Pseudomonas sp. H1R1, isolated from the effluent channels of mariculture, was identified as a novel salt-tolerant heterotrophic nitrification-aerobic denitrification (HN-AD) bacterium, and its potential for nitrogen removal was assessed. The results showed that when succinate was used as the optimal carbon source, H1R1 achieved nitrate and total nitrogen removal efficiencies of over 90% under conditions of pH 7, dissolved oxygen (DO) concentration of 1.2–2.0 mg/L, and an initial NO 3 − -N concentration of 138 mg/L. Under continuous operation, the Pseudomonas sp. H1R1- Chlorella marina consortium outperformed the Pseudomonas -monoculture configuration in eliminating chemical oxygen demand (COD) and total nitrogen (TN) from mariculture wastewater. Carbon-cycle analysis revealed significant up-regulation of glycolysis, the tricarboxylic acid (TCA) cycle, and the Nathan Entner and Michael Doudoroff (ED) pathway, indicating enhanced organic-matter degradation through bacterium-algae synergy. Further analysis of nitrogen cycle characteristics confirmed that the relative abundances of genes associated with aerobic denitrification and the production of N 2 O and NO were reduced in the consortium, which thus endows it with the potential to mitigate greenhouse gas emissions.