SOM genesis: microbial biomass as a significant source
SOM genesis: microbial biomass as a significant source
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DOI：
10.1007/s10533-011-9658-z
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发表时间：
2012-11-01
期刊：
影响因子：
4
通讯作者：
Kaestner, Matthias
中科院分区：
文献类型：
--
作者：
Miltner, Anja;Bombach, Petra;Kaestner, Matthias
土壤有机质(SOM)的适当管理是维持土壤肥力和减缓全球大气二氧化碳浓度上升所必需的，并应通过了解SOM的来源、空间组织和稳定过程来了解。近年来，微生物量残留物(即坏死体)已被确定为土壤有机质的重要来源。在这里，我们认为细菌和真菌的细胞壁被膜稳定在土壤中，并对小颗粒SOM的形成做出重大贡献。这一假设是基于C-13标记细菌细胞的土壤培养实验的质量平衡和扫描电子显微镜(SEM)对微生物残留物的可视化。在224天的培养结束时，50%的生物量来源的C保留在土壤中，主要是在SOM的非生物部分(40%的添加的生物量C)。扫描电子显微镜下很少见完整的细胞。相反，200-500 nm大小的有机片状碎片丰富，这些碎片与细胞被膜腐烂和碎裂的各个阶段有关。类似的碎片，在暴露在地下水中的最初清洁和无菌的原位微观世界中形成，为它们在微生物生长和表面定居过程中的形成提供了明确的证据。因此，微生物细胞被膜片段对SOM的形成有很大的贡献。SOM的这种起源和相关的大分子结构与大多数关于SOM的观察结果是一致的，包括丰富的微生物衍生生物标志物、低C/N比、憎水性和生物分子的稳定性，这些在理论上应该很容易被降解。
Proper management of soil organic matter (SOM) is needed for maintaining soil fertility and for mitigation of the global increase in atmospheric CO2 concentrations and should be informed by knowledge about the sources, spatial organisation and stabilisation processes of SOM. Recently, microbial biomass residues (i.e. necromass) have been identified as a significant source of SOM. Here, we propose that cell wall envelopes of bacteria and fungi are stabilised in soil and contribute significantly to small-particulate SOM formation. This hypothesis is based on the mass balance of a soil incubation experiment with C-13-labelled bacterial cells and on the visualisation of the microbial residues by means of scanning electron microscopy (SEM). At the end of a 224-day incubation, 50% of the biomass-derived C remained in the soil, mainly in the non-living part of SOM (40% of the added biomass C). SEM micrographs only rarely showed intact cells. Instead, organic patchy fragments of 200-500 nm size were abundant and these fragments were associated with all stages of cell envelope decay and fragmentation. Similar fragments, developed on initially clean and sterile in situ microcosms during exposure to groundwater, provide clear evidence for their formation during microbial growth and surface colonisation. Microbial cell envelope fragments thus contribute significantly to SOM formation. This origin and the related macromolecular architecture of SOM are consistent with most observations on SOM, including the abundance of microbial-derived biomarkers, the low C/N ratio, the water repellency and the stabilisation of biomolecules, which in theory should be easily degradable.