Formation of biogenic non-extractable residues from pesticides: metabolic and environmental conditions and their potential implications for risk assessment (FormNER)

先前的DFG项目结果表明，由易于生物降解的农药（2,4- d、草甘膦和亚胺磷）形成的不可提取残留物（NER）主要含有生物源性NER （bioNER）。BioNER可以是直接从农药中吸收C (N)的结果，也可以是通过二氧化碳固定和矿化N同化到最终稳定在土壤或沉积物有机质（OM）中的微生物生物量中间接吸收C的结果。农药的周转和生物分子的形成可能受外部环境条件、土壤特征或内部微生物代谢途径的控制，这取决于生物体的营养状况；然而，这些过程在不同土壤特别是不同气候条件下的可变性尚未得到分析。此外，类似的转换过程也可能发生在植物中，但到目前为止还没有详细的研究。因此，本项目的总体目标是研究不同代谢和环境条件下以及不同土壤中农药的周转，包括生物离子的形成和标记二氧化碳的固定。环境条件（温度，pH值，OM）或土壤类型对两种全球最畅销的农药（2,4- d和草甘膦）降解的影响将在德国（温带气候）和哥伦比亚（热带气候）土壤中进行比较。代谢条件（饥饿与生长条件）对生物分子形成的影响将通过计算氨基酸与氨基糖的比例和鉴定活性降解物中的蛋白质来确定。将研究与几种农药类（如三嗪或三嗪酮）相关的高度氧化碳原子通过二氧化碳固定间接形成生物氧化物，并与N吸收有关。在植物细胞中，预计与土壤和沉积物中相似的内能物质形成过程和农药的周转路线；因此，这些过程也与食品中的农药残留有关。在这种情况下，几种农药的代谢和生物分子形成将在植物细胞悬浮培养中作为第一种方法进行研究。因此，该项目将向综合评估农药命运迈出第一步，包括在土壤和植物细胞中的转化，从而评估粮食作物的环境风险和毒理学危害。

Results of a previous DFG project show that non-extractable residues (NER) formed from easily biodegradable pesticides (2,4-D, glyphosate and metamitron) mainly contain biogenic NER (bioNER). BioNER can be a result of a direct assimilation of C (N) from the pesticide or indirect incorporation of C via CO2 fixation and assimilation of mineralised N into the microbial biomass ultimately stabilised in the organic matter (OM) of soil or sediments. The pesticide turnover and bioNER formation is presumably controlled by external environmental conditions, soil characteristics or internal microbial metabolic pathways depending on the nutritional status of the organisms; however, the variability of these processes in different soils particularly from different climates were not analysed yet. In addition, similar turnover processes may also occur in plants, but they have not been investigated in detail so far.The overall goal of the present project is thus to investigate the turnover of pesticides under different metabolic and environmental conditions and in different soils including the bioNER formation and the fixation of labelled CO2. The impact of environmental conditions (temperature, pH, OM) or soil type on the degradation of two globally best-selling pesticides (2,4-D and glyphosate) will be investigated in German (temperate climate) and Colombian (tropical climate) soils for comparison. The impact of metabolic conditions (starvation versus growth conditions) on bioNER formation will be determined by the calculation of the ratios of amino acids to amino sugars and by identification of proteins from the active degraders. Indirect formation of bioNER via CO2 fixation from the highly oxidised carbon atoms relevant for several pesticide classes (e.g. triazines or triazinones) will be studied and related to N uptake. Similar processes of NER formation and turnover routes of pesticides as in the soil and sediment are expected in the plant cells; these processes are thus also relevant for pesticide residues in food. In this context, the metabolisation and bioNER formation of several pesticides will be investigated in plant cell suspension cultures as a first approach. The project will therefore provide a first step towards an integrated assessment of pesticide fate including transformation in soils and in plant cells and thus of environmental risk and toxicological hazard of food crops.