Utilisation and transformation of organic and inorganic nitrogen by soil microorganisms and its regulation by excessive carbon and nitrogen availability

• Published in: Biology and fertility of soils Vol. 59; no. 4; pp. 379 - 389
• Main Authors: Pan, Wankun, Zhou, Jingjie, Tang, Sheng, Wu, Lianghuan, Ma, Qingxu, Marsden, Karina A., Chadwick, David R., Jones, Davey L.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.05.2023; Springer Nature B.V
• Subjects: Agriculture; Availability; Biomedical and Life Sciences; Carbon; Complex compounds; Cytoplasm; Glycine; Glycine (amino acid); Life Sciences; microbiome; Microbiomes; Microorganisms; Mineralization; Nitrification; Nitrogen; Nitrogen isotopes; Original Paper; Soil; Soil microorganisms; Soil Science & Conservation; Soils; Uptake; Isotopic labelling; Organic nitrogen uptake; Inorganic nitrogen uptake; C and N bioavailability
• ISSN: 0178-2762; 1432-0789
• DOI: 10.1007/s00374-023-01712-w

The process of nitrogen (N) transformation after microbial utilisation of organic and inorganic N is unclear. 15 N -glycine (Gly), 15 NH 4 + and 15 NO 3 − were used to investigate the uptake, release and reutilisation of N by microorganisms over 9 days. In addition, high amounts of unlabelled carbon (C) or N were added to explore how C or N availability affects the cycling of inorganic and organic N by microorganisms. Within 15 min, 67% of the added 15 N-Gly was taken up by soil microorganisms; within 1 h, 8% was released as NH 4 + . The released 15 NH 4 + was reutilised by the microorganisms within hours. Microorganisms took up 50% of the added 15 NH 4 + (15 min) and released 13% of the taken up NH 4 + (1 h). Microorganisms prefer to take up Gly rather than NH 4 + because they can directly acquire C from Gly for maintaining its growth and synthesising more complex compounds. NO 3 − was taken up by microorganisms within minutes but not released into the soil. NO 3 − was likely stored in the cytoplasm, to be used as an N source to face future N-deficient environments. When high concentrations of C or N were added, the assimilation of Gly and NH 4 + increased, whereas N mineralisation and nitrification rates decreased, and the uptake of NO 3 − remained stable. Overall, Gly and NH 4 + were taken up, released and re-taken up by microorganisms and were preferentially utilised under excess C or N sources, while NO 3 − was stored in the microbiome. These findings provide new insights into N uptake by microorganisms in short-term.