Role of natural nanoparticles and colloids for the mobility and bioavailability of antibiotics in soil

天然胶体，包括纳米颗粒，在环境中无处不在，通常是抗生素等药物的重要载体。然而，几乎没有人知道废水处理和土壤类型如何调节胶体的流行，从而调节胶体相关抗生素的流行。此外，胶体对土壤中抗生素生物利用度的影响仍不清楚。我们假设i）废水、土壤和土壤流出物中的大部分抗生素与胶体结合，ii）废水质量的变化以及iii）不同的土壤类型改变胶体的组成以及与之结合的抗生素的部分。我们进一步假设，iv）抗生素与胶体的结合降低了它们的生物利用度，因此，抗生素抗性基因的选择，而v）植物吸收可能不受废水处理的影响，因为经处理的废水中的抗生素浓度可能低于未经处理的水中的抗生素浓度，但更容易获得。为了验证这些假设，我们将i）分析未经处理的废水、土壤和柱的土壤流出物的胶体和真正溶解相中的抗生素以及黑土的田间实验。我们将ii）通过分析抗生素在真正溶解的和在用未经处理的或经处理的废水灌溉的柱和田间实验中的土壤的胶体相中的抗生素，评估由废水质量变化引起的抗生素与胶体的关联的变化，以及iii）将分析扩展到轻质土和变性土（柱实验）。进行卫星实验以评估iv）模型土壤胶体对抗生素抗性基因与SP 3的选择的影响，其中我们将确定在不存在和存在这些胶体的情况下含有不同抗生素浓度的肉汤中细菌的最小抑制浓度和生长曲线。为了包括来自不同土壤类型的具有不同胶体组成的真实土壤，我们还将使用中心孵育实验的真正溶解和胶体部分中的等基因抗性和敏感菌株来确定抗生素浓度以及SP 3的最小选择性浓度。v）最终在中心柱和田间实验中监测植物吸收。为了获得关于抗生素结合的单个胶体成分的作用的信息，我们将使用不对称场流分级法确定所有废水和土壤样品的胶体尺寸范围和组成。将胶体-抗生素相互作用的这一信息与其他项目的大量土壤浓度（SP 2）和微生物参数联系起来，为首次了解天然胶体在废水灌溉土壤中抗生素流动性和生物利用度方面的作用提供了独特的机会。

Natural colloids, including nanoparticles are ubiquitous in the environment and often important carriers for pharmaceuticals like antibiotics. However, almost nothing is known about how wastewater treatment and soil type modulate the prevalence of colloids and thus of colloid-associated antibiotics. Further, the effects of colloids on bioavailability of antibiotics in soil remain unclear. We hypothesize that i) large parts of antibiotics in wastewater, soil and soil effluent are bound to colloids, and that ii) a change in wastewater quality as well as iii) different soil types alter the composition of colloids as well as the portion of antibiotics bound to them. We further assume that iv) binding of antibiotics to colloids reduces their bioavailability and, accordingly, the selection of antibiotic resistance genes, while v) plant uptake is likely not influenced by wastewater treatment, as antibiotic concentrations in treated wastewater are likely lower but more available than in untreated water. To test these hypotheses, we will i) analyze antibiotics in the colloidal and truly dissolved phase of untreated wastewater, soil and soil effluent of the column and field experiment of the Phaeozem. We will ii) assess changes in the association of antibiotics with colloids as induced by changes in wastewater quality by analyzing antibiotics in the truly dissolved and in the colloidal phase of soils in the column and field experiment irrigated with untreated or treated wastewater, and iii) extend the analyses to to Leptosols and Vertisols (column experiment). A satellite experiment is performed to assess iv) effects of model soil colloids on the selection of antibiotic resistance genes together with SP 3, where we will determine minimum inhibitory concentrations and growth curves for bacteria in broths containing different antibiotic concentrations in the absence and presence of these colloids. To include real-soils with different colloid compositions from different soil types, we will also determine antibiotic concentrations as well as with SP 3 the minimal selective concentrations using isogenic resistant and susceptible strains in the truly dissolved and colloidal fraction of the central incubation experiment. v) Plant uptake is finally monitored in both central column and field experiments. To obtain information about the role of single colloidal constituents for antibiotic binding we will determine colloidal size ranges and composition using asymmetric Field Flow Fractionation for all wastewater and soil samples. Linking this information of colloid-antibiotics interactions to bulk soil concentrations (SP 2) and microbiological parameters from the other projects provides a unique chance to understand for the very first time the role of natural colloids for antibiotic mobility and bioavailability in soil under wastewater irrigation.