Fate of low molecular weight organic substances in an arable soil: From microbial uptake to utilisation and stabilisation
Fate of low molecular weight organic substances in an arable soil: From microbial uptake to utilisation and stabilisation
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DOI：
10.1016/j.soilbio.2014.06.029
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发表时间：
2014-10-01
影响因子：
9.7
通讯作者：
Kuzyakov, Yakov
中科院分区：
文献类型：
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作者：
Gunina, Anna;Dippold, Michaela A.;Kuzyakov, Yakov
微生物的吸收和利用是低分子有机物在土壤中转化的主要途径，但有关转化的细节还很有限。由于不同的LMWOS在不同的步骤进入生化循环，我们假设它们的碳(C)结合到微生物生物量中并因此在土壤中稳定的百分比是不同的。在田间试验中，LMWOS的三个主要基团：氨基酸(丙氨酸、谷氨酸)、糖(葡萄糖、核糖)和羧酸(醋酸酯、棕榈酸酯)以自然发生的浓度被施入壤质可耕种的路维素中。在应用后3d和10d，研究了这些LMWOS将C-13掺入可提取微生物生物量(EMB)和磷脂脂肪酸(PLFA)中的情况。通过用C-13.35取代PLFA-C来评估微生物利用低分子量有机硅构建细胞膜的情况。试验10天后，土壤有机质组成中仍有80%的低分子量碳-13存在于土壤有机质中，C-13在第3天进入EMB的比例为10-24%，在第10天为1-15%。C-13在EMB中的掺入量最大，氨基酸最少。主要在第10天观察到不同LMWO之间微生物利用的显著差异。因此，尽管微生物最初快速吸收，但微生物细胞内的进一步代谢决定了不同LMWO中C在土壤中的具体去向。每个LMWO中的C-13被整合到每个PLFA中。这反映了所有功能微生物群对所有低分子量有机化合物的普遍利用。棕榈酸酯优先加入到PLFA中反映了它作为脂肪酸直接前体的作用。与谷氨酸、核糖和醋酸酯相比，丙氨酸和葡萄糖在特定PLFA中的C-13掺入量更高，反映了糖酵解衍生物质在脂肪酸合成中的优先使用。革兰氏阴性菌(16：1 omega 7c和18：1 omega 7c)在LMWOS的利用中最丰富和最活跃。它们的高活性对应于对合成代谢产物的高需求，例如，戊糖-磷酸途径的优势，即核糖-C掺入PLFA。从糖和氨基酸到丝状微生物的C-13参入率低于所有原核生物。然而，对于羧酸，掺入范围与革兰氏阳性菌相同(0.1-0.2%的羧酸C-13)。这可能反映了真菌和其他丝状微生物在利用酸性和复杂有机物质方面的优势。因此，我们表明，尽管初始吸收相似，但来自单个LMWOS的C遵循不同的代谢路径，这解释了LMWOS-C在10天内的个体命运。因此，土壤中碳的稳定主要与其在不同稳定性的微生物化合物中的结合有关，而与其最初的微生物吸收无关。(C)2014爱思唯尔有限公司。保留所有权利。
Microbial uptake and utilisation are the main transformation pathways of low molecular weight organic substances (LMWOS) in soil, but details on transformations are strongly limited. As various LMWOS classes enter biochemical cycles at different steps, we hypothesize that the percentage of their carbon (C) incorporation into microbial biomass and consequently stabilisation in soil are different.Representatives of the three main groups of LMWOS: amino acids (alanine, glutamate), sugars (glucose, ribose) and carboxylic acids (acetate, palmitate) - were applied at naturally-occurring concentrations into a loamy arable Luvisol in a field experiment. Incorporation of C-13 from these LMWOS into extractable microbial biomass (EMB) and into phospholipid fatty acids (PLFAs) was investigated 3 d and 10 d after application. The microbial utilisation of LMWOS for cell membrane construction was estimated by replacement of PLFA-C with C-13.35-80% of initially applied LMWOS-C-13 was still present in the composition of soil organic matter after 10 days of experiment, with 10-24% of C-13 incorporation into EMB at day three and 1-15% at day 10. Maximal incorporation of C-13 into EMB was observed from sugars and the least from amino acids. Strong differences in microbial utilisation between LMWOS were observed mainly at day 10. Thus, despite similar initial rapid uptake by microorganisms, further metabolism within microbial cells accounts for the specific fate of C from various LMWOS in soils.C-13 from each LMWOS was incorporated into each PLFA. This reflects the ubiquitous utilisation of all LMWOS by all functional microbial groups. The preferential incorporation of palmitate into PLFAs reflects its role as a direct precursor for fatty acids. Higher C-13 incorporation from alanine and glucose into specific PLFAs compared to glutamate, ribose and acetate reflects the preferential use of glycolysis-derived substances in the fatty acids synthesis.Gram-negative bacteria (16:1 omega 7c and 18:1 omega 7c) were the most abundant and active in LMWOS utilisation. Their high activity corresponds to a high demand for anabolic products, e.g. to dominance of pentose-phosphate pathway, i.e. incorporation of ribose-C into PLFAs. The C-13 incorporation from sugars and amino acids into filamentous microorganisms was lower than into all prokaryotic groups. However, for carboxylic acids, the incorporation was in the same range (0.1-0.2% of the applied carboxylic acid C-13) as that of gram-positive bacteria. This may reflect the dominance of fungi and other filamentous microorganisms for utilisation of acidic and complex organics.Thus, we showed that despite similar initial uptake, C from individual LMWOS follows deviating metabolic pathways which accounts for the individual fate of LMWOS-C over 10 days. Consequently, stabilisation of C in soil is mainly connected with its incorporation into microbial compounds of various stability and not with its initial microbial uptake. (C) 2014 Elsevier Ltd. All rights reserved.