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1. Quantification of biological nitrogen fixation by Mo-independent complementary nitrogenases in environmental samples with low nitrogen fixation activity

   https://doi.org/10.1038/s41598-022-24860-9  

   Haynes, Shannon J. ; Darnajoux, Romain ; Han, Eunah ; Oleynik, Sergey ; Zimble, Ezra ; Zhang, Xinning ( December 2022 , Scientific Reports)

   Biological nitrogen fixation (BNF) by canonical molybdenum and complementary vanadium and iron-only nitrogenase isoforms is the primary natural source of newly fixed nitrogen. Understanding controls on global nitrogen cycling requires knowledge of the isoform responsible for environmental BNF. The isotopic acetylene reduction assay (ISARA), which measures carbon stable isotope (¹³C/¹²C) fractionation between ethylene and acetylene in acetylene reduction assays, is one of the few methods that can quantify isoform-specific BNF fluxes. Application of classical ISARA has been challenging because environmental BNF activity is often too low to generate sufficient ethylene for isotopic analyses. Here we describe a high sensitivity method to measure ethylene δ¹³C by in-line coupling of ethylene preconcentration to gas chromatography-combustion-isotope ratio mass spectrometry (EPCon-GC-C-IRMS). Ethylene requirements in samples with 10% v/v acetylene are reduced from > 500 to ~ 20 ppmv (~ 2 ppmv with prior offline acetylene removal). To increase robustness by reducing calibration error, single nitrogenase-isoformAzotobacter vinelandiimutants and environmental sample assays rely on a common acetylene source for ethylene production. Application of the Low BNF activity ISARA (LISARA) method to low nitrogen-fixing activity soils, leaf litter, decayed wood, cryptogams, and termites indicates complementary BNF in most sample types, calling for additional studies of isoform-specific BNF.

    

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2. Biological Nitrogen Fixation Does Not Replace Nitrogen Losses After Forest Fires in the Southeastern Amazon

   https://doi.org/10.1007/s10021-019-00453-y  

   Wong, Michelle Y. ; Neill, Christopher ; Marino, Roxanne ; Silvério, Divino V. ; Brando, Paulo M. ; Howarth, Robert W. ( August 2020 , Ecosystems)
3. Biological nitrogen fixation by alternative nitrogenases in terrestrial ecosystems: a review

   https://doi.org/10.1007/s10533-020-00666-7  

   Bellenger, J. P. ; Darnajoux, R. ; Zhang, X. ; Kraepiel, A. M. ( May 2020 , Biogeochemistry)
4. Biological nitrogen fixation detected under Antarctic sea ice

   https://doi.org/10.1038/s41561-020-00651-7  

   Shiozaki, Takuhei ; Fujiwara, Amane ; Inomura, Keisuke ; Hirose, Yuu ; Hashihama, Fuminori ; Harada, Naomi ( November 2020 , Nature Geoscience)
5. Mineral-Bound Trace Metals as Cofactors for Anaerobic Biological Nitrogen Fixation

   https://doi.org/10.1021/acs.est.3c01371  

   Sheng, Yizhi ; Baars, Oliver ; Guo, Dongyi ; Whitham, Jason ; Srivastava, Shreya ; Dong, Hailiang ( April 2023 , Environmental Science & Technology)