Fe(III)-dependent Nrf activity determines nitrate reduction partitioning in nitrate-reducing communities.
Ji Zhan1, Lu Zhang1, Shuyao Lai1
1Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, China.
Mbio
|September 30, 2025
Summary
Iron availability (Fe(III)) controls microbial nitrogen cycling, favoring dissimilatory nitrate reduction to ammonium (DNRA) when abundant and denitrification when scarce. This discovery offers new strategies for managing nitrogen loss in ecosystems.
Area of Science:
- Microbial Ecology
- Environmental Microbiology
- Biogeochemistry
Background:
- Nitrogen loss from ecosystems via microbial processes like denitrification impacts agriculture and contributes to greenhouse gas emissions.
- Dissimilatory nitrate reduction to ammonium (DNRA) offers a pathway for nitrogen retention, but factors controlling its prioritization over denitrification are not fully understood.
- Environmental nutrient status, such as the carbon-to-nitrogen ratio, is traditionally considered the primary driver of nitrate reduction pathways.
Purpose of the Study:
- To investigate the role of Fe(III) availability in regulating nitrate reduction partitioning between DNRA and denitrification.
- To elucidate the microbial mechanisms governing Fe(III)-dependent nitrate reduction pathways in a co-culture system.
- To validate the effect of Fe(III) on DNRA activity in natural environmental samples.
Main Methods:
- Culturing of *Geobacter metallireducens* and *Alcaligenes faecalis* co-cultures under varying Fe(III) availability.
- Monitoring of nitrogen conversion dynamics and microbial community composition.
- Enzymatic activity assays (nitrate/nitrite reductase) and gene mutation analyses.
- Experimental validation using urban river water samples.
Main Results:
- Fe(III) availability dictates nitrate reduction pathways: DNRA dominates under Fe(III)-replete conditions (driven by *G. metallireducens*), while denitrification prevails under Fe(III)-depleted conditions (interspecies synergy).
- Nitrite reductase (Nrf) activity in *G. metallireducens* was identified as the key Fe(III)-dependent factor controlling nitrate reduction partitioning.
- Fe(III) supplementation significantly enhanced DNRA activity in urban river water, confirming its regulatory role in situ.
Conclusions:
- Fe(III) is a critical, previously unrecognized regulator of microbial nitrogen retention, influencing the balance between DNRA and denitrification.
- Understanding Fe(III)'s role provides novel strategies for mitigating nitrogen loss in agricultural and aquatic environments.
- This research bridges microbial ecology and environmental management, highlighting trace metal influence on nutrient cycling for ecosystem health.
Keywords:
Fe(III) cofactordenitrificationdissimilatory nitrate reduction to ammoniuminterspecies synergistic denitrificationnitrite reductasenitrogen conversionMore Related Videos
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