Food for microorganisms: Position-specific 13 C labeling and 13 C-PLFA analysis reveals preferences for sorbed or necromass C
Food for microorganisms: Position-specific 13 C labeling and 13 C-PLFA analysis reveals preferences for sorbed or necromass C
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DOI：
10.1016/j.geoderma.2017.09.042
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发表时间：
2018-02
期刊：
影响因子：
6.1
通讯作者：
C. Apostel;J. Herschbach;Ezekiel K. Bore;S. Spielvogel;Y. Kuzyakov;M. Dippold
中科院分区：
文献类型：
--
作者：
C. Apostel;J. Herschbach;Ezekiel K. Bore;S. Spielvogel;Y. Kuzyakov;M. Dippold
矿物表面吸附是土壤有机质稳定的重要过程之一。虽然这种稳定性通常归因于吸附的SOM对微生物的不可访问性，但最近的研究发现，从吸附的底物中可以提高代谢效率。应用13C标记的吸附示踪剂，结合化合物特定的13C分析磷脂脂肪酸(PLFA)，可以确定这种更高的效率是由于a)整个微生物群落的代谢变化，还是b)适应吸附C来源的微生物专家的代谢变化。为了评估单个微生物组中吸附引起的代谢变化，我们将均匀和位置特定的13C标记的丙氨酸添加到壤质路维索尔中，并将土壤样本培养10天。比较了两种不同的改良剂：i)吸附在灭菌土壤上的丙氨酸，以及ii)溶液中的游离丙氨酸。通过~(13)C-PLFA分析对不同微生物类群的丙氨酸结合进行了评价，大多数微生物类群对吸附的丙氨酸和游离态的丙氨酸的吸收是相等的。大多数微生物类群的代谢模式也是相似的：从羧基C-1到PLFA的C可以忽略不计，而来自氨基结合的C-2和甲基C-3的C优先进入PLFA。这种模式反映了C3分子的基本微生物代谢--通过丙酮酸脱羧基快速矿化C-1。只有真菌在其PLFA中结合了更多来自吸附的C而不是游离的丙氨酸。它们的代谢模式也显示出更复杂的代谢过程，即通过葡萄糖异生作用，然后是戊糖-磷酸途径。虽然大多数微生物组的PLFA在10天内保持稳定或下降，但放线杆菌PLFA中的13C从第1天到第10天增加了7倍。放线杆菌13C的强劲增加是因为它们吸收了来自微生物坏死体或分泌产物的次要底物。本实验表明，吸附底物的代谢更有效是微生物专家的工作：虽然统一标记显示吸附底物比游离底物在真菌PLFA中的掺入量更高，为了评估吸附引起的单个微生物群的转化路径的变化，我们以两种方式均匀地和位置地添加-特别是13C和14C标记的丙氨酸-土壤中的一种常见氨基酸：i)吸附到灭菌土壤(壤质路维索尔)上或ii)在溶液中游离，培养10天。通过13C-PLFA分析，在不同的微生物群中评估了丙氨酸单个C位的微生物掺入，大多数微生物群能够平等地吸收吸附的和游离的丙氨酸。大多数微生物类群的代谢模式也保持相似：来自羧基C-1的C几乎不进入PLFA，而来自氨基(C-2)的C和甲基化C-3优先进入微生物的PLFA。这反映了C3分子通过糖酵解的基本微生物代谢。只有真菌在其PLFA中结合了更多来自吸附的C而不是游离的丙氨酸。它们的代谢模式也显示出更复杂的代谢过程，主要是通过糖异生，然后是戊糖-磷酸途径。在所有微生物组的磷脂酸掺入保持稳定或在10天内下降的同时，放线菌中的~(13)C从第1天到第10天增加了7倍。放线菌中~(13)C的这种强劲的增加是…
Sorption to mineral surfaces is one of the most important processes contributing to soil organic matter (SOM) stabilization. While this stabilization is commonly attributed to inaccessibility of the sorbed SOM to microorganisms, recent findings have revealed increased metabolic efficiency from sorbed substrates. The application of position-specifically 13C labeled sorbed tracer, combined with compound-specific 13C analysis of phospholipid fatty acids (PLFA), enables determination of whether this higher efficiency is due to a metabolic shift in a) the whole microbial community or b) microbial specialists adapted to sorbed C sources.To assess metabolic changes induced by sorption in individual microbial groups, we added uniformly and position-specifically 13C labeled alanine to a loamy Luvisol and incubated the soil samples for 10 days. Two different amendments were compared: i) alanine sorbed to sterilized soil, and ii) free alanine in solution. Incorporation of C from individual alanine positions was evaluated in distinct microbial groups classified by 13C-PLFA analysis.Most of the microbial groups took up sorbed and free alanine equally. The metabolic pattern was also similar in most microbial groups: incorporation of C from carboxylic C-1 into PLFA was negligible, whereas C from the amino-bound C-2 and the methyl C-3 were preferentially incorporated into PLFA. This pattern reflects the basic microbial metabolism of C3 molecules - fast mineralization of C-1 via pyruvate decarboxylation. Only fungi incorporated more C from sorbed than free alanine into their PLFA. Their metabolic pattern also revealed a more complex metabolization via gluconeogenesis, followed by pentose-phosphate pathway.While the incorporation into most microbial groups’ PLFA remained stable or decreased over 10 days, the 13C in Actinobacteria PLFA increased up to 7 times from day 1 to day 10. This strong 13C increase in Actinobacteria was explained by their uptake of secondary substrates derived from microbial necromass or secretion products.This experiment showed that the more efficient metabolization of sorbed substrates is the work of microbial specialists: While uniform labeling revealed the higher incorporation of sorbed than free substrate into fungus PLFAs, position-specific labeling allowed the reconstruction of metabolic changes triggered by sorption of the substrate.To assess changes in the transformation pathways of individual microbial groups caused by sorption, we added uniformly and position-specifically 13C and 14C labeled alanine—a common amino acid in soil—in two ways: i) sorbed to sterilized soil (loamy Luvisol) or ii) free in solution, and incubated for 10 days. Microbial incorporation of alanine’s individual C positions was evaluated in distinct microbial groups classified by 13C-PLFA analysis.Most of the microbial groups were able to take up sorbed and free alanine equally. The metabolic pattern also remained similar in most microbial groups: the C from carboxylic C-1 was nearly not incorporated into PLFA, whereas the C from the amino-bound (C-2) and the methylic C-3 were preferentially incorporated into PLFA of microorganisms. This reflects the basic microbial metabolism of C3 molecules via glycolysis. Only fungi incorporated more C from sorbed than free alanine into their PLFA. Their metabolic pattern also revealed a much more complex metabolization via gluconeogenesis, followed by pentose-phosphate pathway.While the incorporation into all microbial groups’ PLFA remained stable or decreased over 10 days, the 13C in Actinomycetes PLFA increased up to 7 times from day 1 to day 10. This strong 13C increase in Actinomycetes was …