Sustained bacterial NO reduction at acidic pH.

Nitrous oxide (NO) is a climate-active gas with emissions predicted to increase due to agricultural intensification. Microbial reduction of NO to dinitrogen (N) is the major consumption process but microbial NO reduction under acidic conditions is considered negligible, albeit strongly acidic soils harbor nosZ genes encoding NO reductase. Here, we study a co-culture derived from acidic tropical forest soil that reduces NO at pH 4.5. The co-culture exhibits bimodal growth with a Serratia sp. fermenting pyruvate followed by hydrogenotrophic NO reduction by a Desulfosporosinus sp. Integrated omics and physiological characterization revealed interspecies nutritional interactions, with the pyruvate fermenting Serratia sp. supplying amino acids as essential growth factors to the NO-reducing Desulfosporosinus sp. Thus, we demonstrate growth-linked NO reduction between pH 4.5 and 6, highlighting microbial NO reduction potential in acidic soils.