Experimental strategies to measure the microbial uptake and mineralization kinetics of dissolved organic carbon in soil
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https://doi.org/10.1007/s42832-020-0035-5
RESEARCH ARTICLE
Experimental strategies to measure the microbial uptake and mineralization kinetics of dissolved organic carbon in soil Baozhen Li1, Tida Ge1 ,*, Paul W. Hill2, Davey L. Jones2, Zhenke Zhu1, Mostafa Zhran1,3, Jinshui Wu1,4 1 Key Laboratory of Agro-ecological Processes in Subtropical Region & Changsha Research Station for Agricultural and Environmental Monitoring, Institute of Subtropical Agriculture, Chinese Academy of Sciences, ChangSha 410125, China 2 School of the Environment and Natural Resoures, University of Wales, Bangor, Gwynedd LL57 2UW, UK 3 Soil and Water Research Department, Nuclear Research Center, Atomic Energy Authority, Abou-Zaabl, 13759, Egypt 4 University of Chinese Academy of Sciences, Beijing 100049, China
ARTICLE INFO
ABSTRACT
Article history:
Soil organic matter turnover rates are typically estimated from mass loss of the material over
Received January 3, 2020
time or from on rates of carbon dioxide production. In the study, we investigated a new way to
Revised April 10, 2020 Accepted April 19, 2020
characterize the concentration-dependent kinetics of amino acids used by measuring microbial uptake and mineralization of solution after additions
Keywords: 14
C tracer
14
14
C-alanine. We measured the depletion from soil
C-alanine. The microbial uptake of
14
C-alanine from soil solution
was concentration-dependent and kinetic analysis indicated the operation of at least three distinct alanine transport systems of differing affinities. Most of the
14
C-alanine depletion from
Microbial uptake
the soil solution occurred rapidly within the first 10–30 min of the incubation after 10 μM to 1
Carbon mineralization Turnover
mM substrate additions. At alanine concentrations less than 250 mM, the kinetic parameters for Km and Vmax of the higher-affinity transporter were 60.0 μM and 1.32 μmol g – 1 DW soil h – 1, respectively. The mineralization of alanine was determined and the half-time values for the rapid mineralization process were 45 min to 1.5 h after the addition at alanine concentrations below 1 mM. The time delay after its uptake into microbial biomass suggested that alanine uptake and subsequent respiration were uncoupled pattern. The microbial N uptake rate was calculated by microbial mineralization, and an estimated Km value of 1731.7± 274.6 μM and Vmax value of 486.0±38.5 μmol kg – 1 DW soil h – 1. This study provides an alternative approach for measuring the rate of turnover of compounds that turnover very rapidly in soil. © Higher Education Press 2020
1 Introduction
* Corresponding author E-mail address: [email protected] (T.D. Ge)
Soil organic matter (SOM) is a very important carbon (C) sink in terrestrial ecosystem, and research on SOM transformation has increased our understanding of the C cycle in soil biogeochemistry. Macromolecular SOM needs to be degraded into low molecular weight organic substances
2
(LMWOS) by enzymes that act as sinks and source of nutrients; and transformation of LMWOS is a key proce
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