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

包括纳米颗粒在内的天然胶体在环境中无处不在，通常是抗生素等药物的重要载体。然而，关于废水处理和土壤类型如何调节胶体的流行以及与胶体相关的抗生素，几乎一无所知。此外，胶体对抗生素在土壤中的生物利用度的影响尚不清楚。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)不同土壤类型改变了胶体的组成以及与它们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，从而降低了抗生素抗性基因的选择，而v)植物的吸收可能不受废水处理的影响，因为处理过的废水中的抗生素浓度可能较低，但比未经处理的水中更有效。为了验证这些假设，我们将i)分析未经处理的废水、土壤和土壤流出物的胶体相和真溶解相中的抗生素，以及Phaeozem的柱和现场实验。我们将ii)评估由废水质量变化引起的抗生素与胶体关系的变化，通过在柱状和田间试验中分析土壤中真正溶解和胶体阶段的抗生素，以及在未经处理或处理的废水灌溉中，iii)将分析扩展到Leptosols和versols（柱状实验）。通过卫星实验来评估模型土壤胶体和SP 3对抗生素抗性基因选择的影响，我们将确定在没有和存在这些胶体的情况下，细菌在含有不同抗生素浓度的肉汤中的最低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成分的真实土壤，我们还将在中心孵育实验的真正溶解和胶体部分中使用等基因抗性和敏感菌株确定抗生素浓度以及SP 3的最小选择浓度。v)最后在中心柱和田间试验中监测植物的吸收。为了获得关于单个胶体成分在抗生素结合中的作用的信息，我们将对所有废水和土壤样品使用不对称场流分选来确定胶体的大小范围和组成。将胶体-抗生素相互作用的信息与散装土壤浓度（SP 2）和其他项目的微生物参数联系起来，提供了一个独特的机会，首次了解天然胶体在废水灌溉下土壤中抗生素流动性和生物利用度的作用。

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.