Sustained bacterial N₂O reduction at acidic pH

Area of Science:

• Environmental microbiology
• Biogeochemistry
• Soil science

Background:

• Nitrous oxide (N₂O) is a potent greenhouse gas with increasing emissions from agriculture.
• Microbial N₂O reduction to N₂ is a key removal pathway, but often considered negligible in acidic environments.
• Acidic soils contain nosZ genes, suggesting potential for N₂O reduction.

Purpose of the Study:

• To investigate microbial N₂O reduction under acidic conditions.
• To characterize a microbial co-culture from acidic tropical forest soil capable of N₂O reduction.
• To elucidate the mechanisms and interactions enabling N₂O consumption in acidic environments.

Main Methods:

• Isolation and cultivation of a microbial co-culture from acidic tropical forest soil.
• Physiological characterization of N₂O reduction activity at low pH.
• Integrated omics (genomics, transcriptomics, proteomics) and metabolic analyses.
• Pyruvate fermentation and hydrogenotrophic N₂O reduction assays.

Main Results:

• A co-culture, comprising Serratia sp. and Desulfosporosinus sp., effectively reduced N₂O at pH 4.5.
• The co-culture exhibited bimodal growth, with Serratia sp. fermenting pyruvate and Desulfosporosinus sp. performing hydrogenotrophic N₂O reduction.
• Interspecies interactions were identified, with Serratia sp. providing essential amino acids to Desulfosporosinus sp.
• Growth-linked N₂O reduction was observed across a pH range of 4.5 to 6.

Conclusions:

• Microbial N₂O reduction is feasible and significant in acidic soils.
• Co-culture dynamics and interspecies nutritional exchange are crucial for N₂O consumption in acidic environments.
• These findings highlight previously underestimated microbial N₂O mitigation potential in acidic ecosystems.