Galactosamine can be used as an indicator for microbial extracellular polymeric substances (EPS), an important source of stable organic matter in agricultural soils

半乳糖胺可用作微生物胞外聚合物（EPS）的指示剂，EPS是农业土壤中稳定有机质的重要来源

• 批准号: 464850637
• 负责人: Dr. Jens Dyckmans
• 金额: --
• 依托单位: Kompetenzzentrum Stabile Isotope
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/464850637?language=en
• 关键词: Galactosamine; used; indicator; microbial; extracellular

Four experiments form a consecutive programme for elucidating the role of EPS (extracellular polymeric substances) in agricultural soil environments, based on the following two central hypotheses: (1) EPS are an important component of microbial necromass, which can be extracted from soil with cation exchange resins (CER). (2) Galactosamine (GalN) indicates microbial EPS in soil. In the first experiment, microbial EPS formation will be investigated by cultivating soil bacteria and soil fungi, using glycerol and starch as a C source in the absence or presence of SOM-free sterile sand. In the second experiment, simple (glycerol or maize-derived starch) and complex (maize-derived cellulose or maize straw) 13C labelled substrates will be tested for their ability to form bacterial and fungal EPS in four soils, differing in their fungi to bacteria ratio due to differences in soil pH and fertilization history. In the third experiment, glucose and cellulose decomposition will be monitored to investigate carbon use efficiency (CUE) and thermodynamic efficiency in two soils, differing in their fungi to bacteria ratio due to differences in fertilization history and due to the absence or presence of EPS. In the fourth experiment, microbial EPS formation in soil will be induced by applying to one soil a simple and easily available substrate (maize-derived starch) that promotes bacterial EPS formation and a more recalcitrant substrate (maize-derived cellulose) that promotes fungal EPS formation. The persistence and aggregate stabilizing effect of the freshly formed EPS will be monitored for 70 days. The C/N ratio of the substrates will be generally adjusted to 40, using (NH4)2SO4 in experiment 1 and (15NH4)2SO4 in experiments 2, 3, and 4. In all experiments, CER extracted EPS will be analysed for their concentration of amino sugars, combined with their compound-specific δ13C and δ13N analysis. EPS extracts will be additionally checked for total organic 13C, total δ15N, total carbohydrates, total protein, and total deoxy-ribonucleic acid (DNA). In the soil, soil organic 13C, microbial biomass 13C, total 15N, microbial biomass 15N, enzyme activity (N-acetyl--D-glucosaminidase and tyrosine-peptidase) and amino sugars will be measured, combined with their compound-specific δ13C and δ13N analysis. In the soil atmosphere, the evolution of total CO2 and 13CO2 will be measured. In experiment 3, heat productions will be additionally monitored using microcalorimetry.

四个实验组成了一个连续的计划，基于以下两个中心假设，阐明了 EPS（细胞外聚合物）在农业土壤环境中的作用：（1）EPS 是微生物坏死物的重要组成部分，可以用阳离子从土壤中提取。 (2)半乳糖胺(GalN)表示土壤中的微生物EPS 在第一个实验中，将通过培养土壤细菌和土壤来研究微生物EPS的形成。真菌，在不存在或存在不含 SOM 的无菌沙的情况下使用甘油和淀粉作为 C 源。在第二个实验中，使用简单（甘油或玉米衍生淀粉）和复杂（玉米衍生纤维素或玉米秸秆）13C 标记底物。将测试它们在四种土壤中形成细菌和真菌 EPS 的能力，由于土壤 pH 值和施肥历史的差异，它们的真菌与细菌的比例有所不同。将监测两种土壤中的碳利用效率 (CUE) 和纤维素分解，由于施肥历史的差异以及 EPS 的存在或不存在，它们的真菌与细菌的比例有所不同。通过在土壤中施用一种简单且容易获得的底物（玉米衍生的淀粉），可以促进细菌 EPS 的形成，以及一种更顽固的底物（玉米衍生的纤维素），可以诱导土壤中形成 EPS。促进真菌 EPS 形成。新形成的 EPS 的持久性和聚集稳定效果将监测 70 天。实验 1 中使用 (NH4)2SO4 和 (15NH4) 底物的 C/N 比通常调整为 40。实验 2、3 和 4 中的 2SO4。在所有实验中，将分析 CER 提取的 EPS 的氨基糖浓度，并结合其化合物特异性δ13​​C 和 δ13N 分析将另外检查土壤中的总有机 13C、总 δ15N、总碳水化合物、总蛋白质和总脱氧核糖核酸 (DNA)、土壤有机物 13C、微生物生物量 13C、总 15N。微生物量15N、酶活性（N-乙酰基-β-D-氨基葡萄糖苷酶和酪氨酸肽酶）和氨基糖将被测量，结合它们的化合物特异性δ13C和δ13N分析在土壤大气中，将测量总CO2和13CO2的演变。 3、将使用微量热法额外监测产热量。