Insights into microbial community, nitrogen‑phosphorus metabolism from metagenomic and metabolomic analysis of microalgal-cyanobacterial consortium-based bioinoculants

The intensification of agriculture through chemical fertilizers has led to severe environmental consequences. This study provides a comprehensive investigation on chemical fertilizer, vermiculite and on microalgal-cyanobacterial consortia (bioinoculants) influencing soil microbial community. Chemical fertilizer application significantly altered the microbial community, suppressing the dominant phylum Proteobacteria to 48.3 % abundance from 60.9 % in the control soil. The bioinoculant treatments maintained a high Proteobacteria abundance (58.9 %-59.7 %) and fostered a growth-oriented, anabolic strategy. The 50:50 mix treatment uniquely promoted the fungal phylum Basidiomycota to 18.2 % abundance and showed the highest investment in the Glycolysis/Gluconeogenesis pathway (23.0 %). Chemical fertilizer treatment upregulated genes for rapid nitrogen assimilation (glnA, Log₂FC = 0.60) and phosphorus starvation response (phoB, Log₂FC = 0.65; pstS, Log₂FC = 0.83). The enhanced energy production and conversion (11.83 %), amino acid transport and metabolism (11.20 %), and fatty acid biosynthesis (45.3 %) was observed in bioinoculant treatment. Unlike chemical fertilizer treatment, bioinoculant treatment led to the accumulation of the osmoprotectant trehalose and structural membrane lipids, while the 50:50 mix was uniquely characterized by a higher abundance of xylose. These findings demonstrate that the microalgal-cyanobacterial consortium can enhance nutrient recycling, and potentially boost soil health by reshaping the soil microbiome and metabolic functions, offering a promising strategy for sustainable agriculture.