15N-amino sugar stable isotope probing (15N-SIP) to trace the assimilation of fertiliser-N by soil bacterial and fungal communities

A - Papers appearing in refereed journals

Reay, M. K., Charteris, A. F., Jones, D. L. and Evershed, R. P. 2019. 15N-amino sugar stable isotope probing (15N-SIP) to trace the assimilation of fertiliser-N by soil bacterial and fungal communities. Soil Biology and Biochemistry. 138 (Article), p. 107599. https://doi.org/10.1016/j.soilbio.2019.107599

AuthorsReay, M. K., Charteris, A. F., Jones, D. L. and Evershed, R. P.

Although amino sugars represent a major component of soil organic nitrogen (ON), the assimilation of nitrate (NO3−) and ammonium (NH4+) into amino sugars (AS) by soil bacteria and fungi represents a neglected aspect of the global N cycle. A deeper knowledge of AS responses to N fertiliser addition may help enhance N use efficiency (NUE) within agricultural systems. Our aim was to extend a sensitive compound-specific 15N-stable isotope probing (SIP) approach developed for amino acids (AAs) to investigate the immobilization of inorganic N
into a range of amino sugars (muramic acid, glucosamine, galactosamine, mannosamine). Laboratory incubations using 15N-ammonium and 15N-nitrate applied at agriculturally relevant rates (190 and 100 kg N ha−1 for 15NH4+ and 15NO3−, respectively) were carried out to obtain quantitative measures of N-assimilation into the AS pool of a grassland soil over a 32-d period. Using gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) we found that δ15N values for individual AS reflected differences in routing of the applied ammonium and nitrate. The contrasting N-assimilation dynamics of bacterial and fungal communities
were demonstrated through determinations of percentage 15N incorporation into diagnostic AS. N-assimilation dynamics of the bacterial community were altered with the applied substrate whilst fungal N-assimilation dynamics were unaffected. Rates and fluxes of the applied N-substrates into the bacterial AS pool reflected known biosynthetic pathways for AS, with fungal glucosamine appearing to be biosynthetically further from the applied substrates than bacterial glucosamine due to different turnover rates. This sensitive and specific compound specific 15N-SIP approach using AS, building on existing approaches with AAs, enables differentiation of N assimilation dynamics within the microbial community and assessment of microbial NUE with agriculturally relevant fertilisation rates.

Keywords15N-stable isotope probing; Microbial immobilization; Nitrogen uptake; Nutrient cycling; Organic matter cycling
Year of Publication2019
JournalSoil Biology and Biochemistry
Journal citation138 (Article), p. 107599
Digital Object Identifier (DOI)https://doi.org/10.1016/j.soilbio.2019.107599
Web address (URL)https://www.sciencedirect.com/science/article/abs/pii/S0038071719302639
Open accessPublished as non-open access
FunderNatural Environment Research Council
Biotechnology and Biological Sciences Research Council
Output statusPublished
Publication dates
Online17 Sep 2019
Publication process dates
Accepted14 Sep 2019

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