Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published October 14, 2023 | Accepted
Discussion Paper Open

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


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.

Copyright and License

The copyright holder for this preprint is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under a CC-BY-NC-ND 4.0 International license.


We thank Colette L. Kelly for valuable guidance and help with the scrambling correction; Nami Kitchen for assistance with IRMS measurements; and Nathan Hart at the Caltech Glass Shop for building the vacuum flasks. We thank the Dr. Tsui-Fen Chou and Baiyi Quan at the Caltech Proteome Exploration Laboratory for assistance with proteomics-based experiments.


National Science Foundation Graduate Research Fellowship Program (RZW), Jane Coffin Childs Memorial Fund for Medical Research Fellowship (ZRL), National Institutes of Health grant R01 HL152190-03 (DKN, JML)


Conceptualization: DKN, JME, RZW, ZRL

Methodology: RZW, ZRL, SAW

Investigation: RZW, ZRL, SAW, DKN

Visualization: RZW, ZRL, DKN, JME

Funding acquisition: DKN, JME, RZW, ZRL

Project administration: DKN

Supervision: DKN, JME

Writing – original draft: RZW, ZRL

Writing – review & editing: RZW, ZRL, DKN, JME

Conflict of Interest

Authors declare that they have no competing interests.

Data Availability

All data are available in the main text or the supplementary materials.

Supplementary Materials

Materials and Methods

Supplementary Text

Figs. S1 to S18

Tables S1 to S13


Files (7.0 MB)
Name Size Download all
6.2 MB Download
805.2 kB Preview Download
13.8 kB Download

Additional details

February 22, 2024
February 22, 2024