Biochemical pathways of amino acids in soil: Assessment by position-specific labeling and 13C-PLFA analysis
Biochemical pathways of amino acids in soil: Assessment by position-specific labeling and 13C-PLFA analysis
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DOI：
10.1016/j.soilbio.2013.08.005
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发表时间：
2013-12-01
影响因子：
9.7
通讯作者：
Kuzyakov, Yakov
中科院分区：
文献类型：
--
作者：
Apostel, Carolin;Dippold, Michaela;Kuzyakov, Yakov
微生物利用是土壤有机质转化的关键过程。首次将位置特异性C-13标记与化合物特异性C-13-PLFA分析相结合，以追踪微生物组中两种氨基酸的代谢产物，并重建详细的生化途径。在田间试验中，通过将位置特异性C-13标记的丙氨酸和谷氨酸施加到土壤中来评估短期转化。氨基酸官能团的微生物利用通过总微生物生物量中的C-13掺入和通过C-13-PLFAdPLFA的高度氧化的两种氨基酸的羧基的损失是最快的，而还原的C位置，例如C3-5，优先掺入微生物和它们的PLFA。从丙氨酸的C-2位置到革兰氏阴性菌的细胞膜中的C的掺入比所有其他微生物组高一个数量级以上。尽管丙氨酸的C-2在第3天仍然结合至C-3，但C-2和C-3位置在第10天部分分裂。相比之下，谷氨酸的C-2从所有微生物组的PLFA中损失得更快。发散指数，这反映了一个位置的相对纳入纳入C从所有位置在一个分子中，揭示了位置之间的歧视是最高的在初始反应，并随着时间的推移而减少。微生物转化pathways.Reconstruction表明，C-2位置的丙氨酸是失去的速度比它的C-3位置，无论该分子是否被用于anabolically或catabolically。谷氨酸C-2仅被八种微生物中的两种（真菌和部分革兰氏阳性原核生物）掺入PLFA中。其在PLFA中的掺入只能通过利用乙二醛旁路或在进入柠檬酸循环之前将谷氨酸转化为天冬氨酸来解释。在这些途径中，没有碳作为CO2损失，但也没有产生能量，使它们成为典型的碳缺乏途径。因此，谷氨酸在细胞生理生态学方面是一种很有前途的代谢示踪剂，从而改变环境条件。通过位置特异性标记分析单个碳原子的命运可以深入了解各种微生物群体利用微生物的机制和动力学。这种方法将大大提高我们对土壤碳通量的理解。(C)2013爱思唯尔有限公司保留所有权利。
Microbial utilization is a key transformation process of soil organic matter (SOM). For the first time, position-specific C-13 labeling was combined with compound-specific C-13-PLFA analysis to trace metabolites of two amino acids in microbial groups and to reconstruct detailed biochemical pathways. Shortterm transformation was assessed by applying position-specifically C-13 labeled alanine and glutamic acid to soil in a field experiment. Microbial utilization of the amino acids' functional groups was quantified by C-13 incorporation in total microbial biomass and in distinct microbial groups classified by C-13-PLFA.Loss from PLFAs was fastest for the highly oxidized carboxyl group of both amino acids, whereas the reduced C positions, e.g. C3-5, were preferentially incorporated into microorganisms and their PLFAs. The incorporation of C from alanines' C-2 position into the cell membrane of gram negative bacteria was higher by more than one order of magnitude than into all other microbial groups. Whereas C-2 of alanine was still bound to C-3 at day 3, the C-2 and C-3 positions were partially split at day 10. In contrast, the C-2 of glutamic acid was lost faster from PLFAs of all microbial groups. The divergence index, which reflects relative incorporation of one position to the incorporation of C from all positions in a molecule, revealed that discrimination between positions is highest in the initial reactions and decreases with time.Reconstruction of microbial transformation pathways showed that the C-2 position of alanine is lost faster than its C-3 position regardless of whether the molecule is used ana- or catabolically. Glutamic acid C-2 is incorporated into PLFAs only by two out of eight microbial groups (fungi and part of gram positive prokaryotes). Its incorporation in PLFA can only be explained by either the utilization of the glyoxolate bypass or the transformation of glutamic acid into aspartate prior to being fed into the citric acid cycle. During these pathways, no C is lost as CO2 but neither is energy produced, making them typical C deficiency pathways. Glutamic acid is therefore a promising metabolic tracer in regard to ecophysiology of cells and therefore changing environmental conditions.Analyzing the fate of individual C atoms by position-specific labeling allows insight into the mechanisms and kinetics of microbial utilization by various microbial groups. This approach will strongly improve our understanding of soil C fluxes. (C) 2013 Elsevier Ltd. All rights reserved.