Soil organic matter turnover rates are typically estimated from mass loss of the material over time or from on rates of carbon dioxide production.In the study,we investigated a new way to characterize the concentratio...Soil organic matter turnover rates are typically estimated from mass loss of the material over time or from on rates of carbon dioxide production.In the study,we investigated a new way to characterize the concentration-dependent kinetics of amino acids used by measuring microbial uptake and mineralization of ^(14)C-alanine.We measured the depletion from soil solution after additions ^(14)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 the soil solution occurred rapidly within the first 10-30 min of the incubation after 10μM to 1 mM substrate additions.At alanine concentrations less than 250μM,the kinetic parameters for K_(m) and V_(max) of the higher-affinity transporter were 60.0μM and 1.32μmol 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 K_(m) value of 1731.7±274.6μM and V_(max )value of 486.0±38.5μmol 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.展开更多
基金financially supported by grants from the National Key Research and Development Program(2016YFE0101100)the Australia-China Joint Research Centre-Healthy Soils for Sustainable Food Production and Environmental Quality(ACSRF48165)+4 种基金the National Natural Science Foundation of China(41522107,41430860)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB15020401)Royal Society Newton Advanced Fellowship(NA150182)Talented Young Scientist Program(TYSP)to Mostafa Zhran supported by China Science and Technology Exchange Center(Egypt-19-004)the State Scholarship Fund of China Scholarship Council(CSC)to Baozhen Li.
文摘Soil organic matter turnover rates are typically estimated from mass loss of the material over time or from on rates of carbon dioxide production.In the study,we investigated a new way to characterize the concentration-dependent kinetics of amino acids used by measuring microbial uptake and mineralization of ^(14)C-alanine.We measured the depletion from soil solution after additions ^(14)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 the soil solution occurred rapidly within the first 10-30 min of the incubation after 10μM to 1 mM substrate additions.At alanine concentrations less than 250μM,the kinetic parameters for K_(m) and V_(max) of the higher-affinity transporter were 60.0μM and 1.32μmol 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 K_(m) value of 1731.7±274.6μM and V_(max )value of 486.0±38.5μmol 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.
