Soil microbial organic nitrogen uptake is regulated by carbon availability

Farrell, Mark, Prendergast-Miller, Miranda, Jones, Davey L., Hill, Paul W. and Condron, Leo M. (2014) Soil microbial organic nitrogen uptake is regulated by carbon availability. Soil Biology and Biochemistry, 77. pp. 261-267. ISSN 0038-0717

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Plants and microorganisms intensely compete for nitrogen (N) at many stages of the terrestrial N cycle. In particular, the dissolved organic N (DON) pool, and competition for low molecular weight dissolved organic N (LMWDON) compounds such as amino acids and peptides (and LMW dissolved organic matter; LMWDOM as a whole) has received significant recent research interest. However, as LMWDON compounds contain both N and carbon (C), a question that remains is whether soil microorganisms are primarily taking up LMWDON mainly for the C or the N contained therein. We investigated microbial uptake rates of the model peptide l-trialanine as a rapidly cycling LMWDON compound in temperate grassland soils of differing fertility using 14C labelling to assess how soil fertility status influenced microbial uptake of LMWDON. We then imposed an excess of C as glucose and/or N as NH4Cl to ask whether the uptake of the peptide was affected by C or N excess. Our results demonstrate that l-trialanine is taken up rapidly from the soil solution (t½ < 1.5 min), and that an excess of C, rather than N, resulted in a reduced uptake of the peptide. From this, we conclude that LMWDON is taken up primarily to fulfil the C requirement of soil microorganisms, indicating that they exist in a C-limited state, and are able to respond quickly to a transient influx of an easily metabolisable resource.

Item Type: Article
Uncontrolled Keywords: Peptide, Grassland soil, 14C, Rapid uptake, Nutrient limitation, Dissolved organic nitrogen
Subjects: C100 Biology
C500 Microbiology
C700 Molecular Biology, Biophysics and Biochemistry
Department: Faculties > Engineering and Environment > Geography and Environmental Sciences
Depositing User: Elena Carlaw
Date Deposited: 03 Sep 2019 10:29
Last Modified: 01 Aug 2021 10:36

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