Arbuscular mycorrhiza suppresses microbial abundance, and particularly that of ammonia oxidizing bacteria, in agricultural soils
- Author: mycolabadmin
- 11/18/2025
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Summary
This study examined how a common soil fungus called arbuscular mycorrhiza affects bacteria and archaea that process ammonia in agricultural soils. Using 50 different soils from the Czech Republic, researchers found that the fungus suppresses ammonia-oxidizing bacteria but not archaea. Interestingly, the fungus actually increased ammonia levels in soil rather than depleting them, suggesting the suppression works through mechanisms beyond simple competition for nutrients.
Background
Arbuscular mycorrhizal (AM) fungi form symbiotic relationships with most terrestrial plants and play crucial roles in nutrient cycling. Ammonia-oxidizing microorganisms compete with AM fungi for ammonium in soils, but their interactions under natural soil conditions remain poorly understood due to high soil variability.
Objective
This study investigated quantitative and compositional responses of indigenous microorganisms in 50 different agricultural soils to actively growing mycelium of the AM fungus Rhizophagus irregularis, particularly focusing on ammonia-oxidizing bacteria (AOB), ammonia-oxidizing archaea (AOA), and comammox Nitrospira.
Results
AM fungal presence systematically suppressed AOB and comammox Nitrospira abundances across diverse soils, while AOA abundance remained unaffected. Surprisingly, AM fungal presence increased soil ammonium levels rather than depleting them, suggesting the suppression mechanism extends beyond direct competition for ammonium.
Conclusion
AM fungi suppress specific ammonia-oxidizing microorganisms, particularly AOB and comammox Nitrospira, but the mechanism likely involves factors beyond simple nutrient competition, possibly including nitrification inhibitors or complex nitrogen cycling pathway interactions.
- Published in:Frontiers in Microbiology,
- Study Type:Experimental Study,
- Source: PMID: 41341498