Widespread detoxifying NO reductases impart a distinct isotopic fingerprint on N₂O under anoxia

Abstract

Nitrous oxide (N₂O), a potent greenhouse gas, can be generated by compositionally complex microbial populations in diverse contexts. Accurately tracking the dominant biological sources of N₂O has the potential to improve our understanding of N₂O fluxes from soils as well as inform the diagnosis of human infections. Isotopic “Site Preference” (SP) values have been used towards this end, as bacterial and fungal nitric oxide reductases produce N₂O with different isotopic fingerprints. Here we show that flavohemoglobin, a hitherto biogeochemically neglected yet widely distributed detoxifying bacterial NO reductase, imparts a distinct SP value onto N₂O under anoxic conditions that correlates with typical environmental N₂O SP measurements. We suggest a new framework to guide the attribution of N₂O biological sources in nature and disease.

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