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

DFG先前的一个项目结果表明，易生物降解农药（2，4-D，草甘膦和苯螨酮）形成的不可提取残留物（NER）主要含有生物源NER（bioNER）。BioNER可以是直接同化农药中的C（N）或通过固定CO2和同化矿化N间接掺入C的结果，最终稳定在土壤或沉积物的有机质（OM）中。农药周转和bioNER的形成可能受外部环境条件、土壤特性或内部微生物代谢途径的控制，具体取决于有机体的营养状况;然而，尚未分析这些过程在不同土壤，特别是不同气候条件下的变异性。此外，类似的周转过程也可能发生在植物中，但他们还没有被详细调查到目前为止，因此，本项目的总体目标是调查农药周转在不同的代谢和环境条件下，在不同的土壤，包括bioNER的形成和固定的标记CO2。将在德国（温带气候）和哥伦比亚（热带气候）土壤中研究环境条件（温度、pH值、有机质）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bioNER形成的影响将通过计算氨基酸与氨基糖的比率以及通过鉴定活性降解物中的蛋白质来确定。间接形成bioNER通过CO2固定从高度氧化的碳原子相关的几个农药类（如三嗪或三嗪酮）将进行研究和相关的氮吸收。预计在植物细胞中，净吸收率的形成过程和农药在土壤和沉积物中的周转途径类似;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bioNER形成将在植物细胞悬浮培养作为第一种方法进行研究。因此，该项目将为综合评估农药的最终结果，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迈出第一步。

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.