Study on the construction of algal-bacterial consortium comprising Pantoea vagans ZHS-1 and Nostoc sp. GD2 and its growth-promoting effect on rice.

Excessive use of chemical fertilizers has led to severe agricultural pollution and soil degradation. Algal-bacterial consortia, as eco-friendly microbial inoculants, offer a promising strategy to reduce fertilizer dependency and promote sustainable agriculture. In this study, we constructed a consortium (ZD-1) comprising the potassium-solubilizing bacterium Pantoea vagans ZHS-1 and the nitrogen-fixing cyanobacterium Desmonostoc muscorum GD2. Co-cultivation at various ratios showed that a 1:1 ratio maximized mutual growth promotion, chemotaxis, and biofilm formation. Under this optimal ratio, the consortium exhibited significantly increased total nitrogen content in BG11 supernatant, as well as enhanced soluble phosphorus and soluble potassium accumulation in specific media containing insoluble P/K sources; these changes were concomitant with upregulation of key functional genes revealed by transcriptomic analysis. Pot experiments demonstrated that ZD-1 inoculation markedly improved rice growth, increased nitrogen, phosphorus, and potassium accumulation in plants, and elevated soil available nutrient contents. Notably, the growth-promoting effect of ZD-1 was comparable to that of full chemical fertilization, and its combination with half-dose fertilizers achieved synergistic yield improvement. Our findings elucidate the molecular interplay between ZHS-1 and GD2 and highlight the potential of the ZD-1 consortium as a viable biofertilizer to partially substitute chemical fertilizers in rice cultivation.IMPORTANCEThis work establishes an optimal algal-bacterial consortium (ZD-1, 1:1 ratio) composed of Pantoea vagans ZHS-1 and Desmonostoc muscorum GD2 with clearly defined synergistic mechanisms. By integrating physiological, biochemical, and transcriptomic analyses, we demonstrate that ZD-1 enhances nutrient transformation, biofilm formation, and plant growth. The consortium effectively increases soil available N, P, and K and substitutes a substantial portion of chemical fertilizers while maintaining rice yield. This study provides a robust theoretical and practical basis for developing green microbial fertilizers and advancing sustainable agriculture.