Summary
This study demonstrates that arbuscular mycorrhizal fungi (AMF) and their associated hyphae significantly reduce denitrification-derived nitrous oxide emissions in organic residue patches through selective recruitment and stimulation of complete denitrifying Pseudomonas bacteria. The mechanism centres on hyphal exudates (carboxylates) acting as chemotactic attractants and gene expression stimulants, specifically upregulating the nosZ gene responsible for N₂O reduction to N₂. The findings, validated through laboratory phenotypic characterisation, controlled inoculation experiments, and an 11-year field study, suggest that exploiting cross-kingdom microbial interactions offers a novel approach to mitigating agricultural greenhouse gas emissions.
UK applicability
The mechanisms identified—AMF-mediated recruitment of denitrifying bacteria—are likely applicable to UK soil and cropping systems, though field validation would be needed under UK climatic and soil conditions. The approach aligns with UK policy interest in nature-based climate mitigation and regenerative agriculture, but adoption would depend on integration with practical farm management and verification of N₂O reduction at commercial scale.
Key measures
N₂O emission reduction (maximum 63%); relative abundance and expression of clade I nosZ, nirS and nirK genes; hyphal length density; Pseudomonas enrichment; citrate cycle gene abundance; nosZ expression upregulation; correlation between hyphal length density and clade I nosZ gene abundance over 11 years
Outcomes reported
The study measured nitrous oxide (N₂O) emissions from residue patches and quantified the abundance and expression of denitrification-related genes (nosZ, nirS, nirK) in the mycorrhizal hyphosphere. It characterised the mechanisms by which arbuscular mycorrhizal fungi recruit N₂O-reducing Pseudomonas bacteria and validated findings through inoculation experiments and an 11-year field trial.
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