Synergistic enhancement of Sorghum bicolor nutrient uptake and growth by EBPR microbiomes and AM fungi

Background Understanding soil microbial interactions is essential for developing biofertilizers in regenerative agriculture. Polyphosphate-accumulating organisms (PAOs) play a pivotal role in enhanced biological phosphorus removal (EBPR) systems by sequestering phosphorus from wastewater and storing it as intracellular polyphosphate. However, their role in terrestrial phosphorus cycling remains poorly characterized, despite their potential to serve as a reservoir of plant-available phosphorus. This study investigates PAO-enriched microbiomes in the sorghum rhizosphere, focusing on their novel interactions with arbuscular mycorrhizal fungi (AMF). By integrating PAOs derived from EBPR biosolids and compost with AMF, we assessed their synergistic effects on plant growth and nutrient uptake in Sorghum bicolor (sorghum), as well as their broader influence on rhizosphere microbial traits and functional dynamics. Results We employed plant biometry analysis, nutrient assays, ³¹P NMR spectroscopy, single-cell Raman microspectroscopy (SCRS), and microbiome profiling to comprehensively evaluate rhizosphere microbial interactions and their effects on plant physiology and nutrient dynamics. ³¹P NMR confirmed polyphosphate accumulation by PAOs derived from both compost and EBPR biosolids, demonstrating the soil adaptability of EBPR-derived PAOs. AMF showed strong synergy with EBPR-derived microbiomes, significantly enhancing sorghum growth, nutrient acquisition, and microbial diversity. Key PAOs, Thauera , Rhodanobacter , and Paracoccus , were successfully incorporated into the rhizosphere and positively correlated with improved phosphorus uptake. PICRUSt2 analysis indicated enrichment of microbial functions linked to motility and xenobiotic metabolism in EBPR-treated rhizospheres. SCRS revealed AMF-induced phenotypic shifts in EBPR-derived microbiomes, while network analysis showed that AMF reorganized community connectivity, fostering novel microbial interactions in EBPR-amended environments. Conclusions This study explored the interactions between AMF and microbiomes derived from EBPR biosolids, in comparison with those from compost, uncovering novel microbial synergies that enhance phosphorus uptake in Sorghum bicolor and promote plant productivity. The findings underscore the potential of targeted microbial co-inoculation such as integrating EBPR microbiomes with AMF as an innovative strategy for improving soil fertility and advancing biofertilizer development through microbial-driven nutrient recycling. By harnessing wastewater-derived phosphorus via PAOs, this approach offers a sustainable alternative to conventional fertilization, supporting regenerative agriculture, nutrient circularity, and the broader application of microbial biofertilizers in crop production.