Biogeochemical transformations of amino acids in soil assessed by position-specific labelling
Biogeochemical transformations of amino acids in soil assessed by position-specific labelling
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DOI：
10.1007/s11104-013-1764-3
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发表时间：
2013-12-01
期刊：
影响因子：
4.9
通讯作者：
Kuzyakov, Yakov
中科院分区：
文献类型：
--
作者：
Dippold, Michaela A.;Kuzyakov, Yakov
土壤氨基酸周转是陆地碳氮循环的重要组成部分。本研究通过独特的位置特异性标记同位素方法追踪它们的驱动力-微生物代谢。使用5个浓度水平的丙氨酸的3个C-14同位素异构体结合选择性灭菌来区分土壤中氨基酸的吸附机制、外酶和微生物利用。吸附和微生物吸收立即发生。非特异性微生物的吸收遵循线性动力学，而能量依赖性的吸收遵循米氏。最初加入的丙氨酸中少于6%被吸附到土壤中，但在微生物转化后，产物以更高的比例（5 - 25%）结合到土壤基质中。羧基（C-1）被微生物迅速氧化，而C-2和C-3位置优先纳入微生物生物量。C代谢对氨基酸浓度的依赖性反映了饥饿、维持和生长条件下的丙氨酸转化途径，本研究表明，位置特异性标记决定了各个功能组的C循环机制和速率。这种方法反映了潜在的代谢途径，并揭示了新有机物质的形成。因此，我们得出结论，位置特异性标记是详细了解亚分子转化途径及其调节因子的独特工具。
Amino acid turnover in soil is an important element of terrestrial carbon and nitrogen cycles. This study accounts for their driver - the microbial metabolism - by tracing them via the unique isotopic approach of position-specific labeling.Three C-14 isotopomers of alanine at five concentration levels combined with selective sterilization were used to distinguish sorption mechanisms, exoenzymatic and microbial utilization of amino acids in soil.Sorption and microbial uptake occurred immediately. Unspecific microbial uptake followed a linear kinetic, whereas energy-dependent uptake followed Michaelis-Menten. Less than 6 % of the initially added alanine was sorbed to soil, but after microbial transformation products were bound to the soil matrix at higher proportions (5-25 %). The carboxyl group (C-1) was rapidly oxidized by microorganisms, whereas C-2 and C-3 positions were preferentially incorporated into microbial biomass. Dependency of C metabolization on amino acid concentration reflected individual alanine transformation pathways for starvation, maintenance and growth conditions.This study demonstrates that position-specific labeling determines the mechanisms and rates of C cycling from individual functional groups. This approach reflected underlying metabolic pathways and revealed the formation of new organic matter. We therefore conclude that position-specific labeling is a unique tool for detailed insights into submolecular transformation pathways and their regulation factors.