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

以往DFG项目的研究结果表明，易生物降解农药(2，4-D、草甘膦和甲胺磷)形成的不可提取残留物(NER)主要含有生物来源的NER(BioNER)。BioNER可以是农药直接同化C(N)的结果，也可以是通过固定CO2间接并入C，并将矿化N同化到最终稳定在土壤或沉积物有机质(OM)中的微生物生物量的结果。农药周转和生物NER的形成可能受到外部环境条件、土壤特性或取决于有机体营养状况的内部微生物代谢途径的控制；然而，这些过程在不同土壤中，特别是来自不同气候的土壤中的变异性尚未得到分析。此外，类似的周转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农药在不同代谢和环境条件下以及在不同土壤中的周转，包括生物NER的形成和标记的CO2的固定。将在德国(温带气候)和哥伦比亚(热带气候)土壤中调查环境条件(温度、pH、OM)或土壤类型对两种全球最畅销农药(2，4-D和草甘膦)降解的影响，以进行比较。代谢条件(饥饿与生长条件)对生物NER形成的影响将通过计算氨基酸与氨基糖的比例以及从活性降解物中鉴定蛋白质来确定。将研究与N吸收有关的几类杀虫剂(如三嗪或三嗪酮)通过高度氧化的碳原子通过二氧化碳固定间接形成生物NER。与土壤和沉积物中农药的形成和周转路线类似，在植物细胞中也有类似的形成和周转过程；因此，这些过程也与食品中的农药残留有关。在此背景下，作为第一种方法，将在植物细胞悬浮培养中研究几种农药的代谢和生物NER的形成。因此，该项目将为综合评估农药的去向迈出第一步，包括在土壤和植物细胞中的转化，从而对粮食作物的环境风险和毒物危害进行评估。

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.