农田土壤中Suls抗性基因对磺胺类抗生素污染响应的构效关系及其机制

Antibiotics have been largely used in human and veterinary medicine, as well as in the feeding of domestic animals. Sulfonamides(SAs) are one of the most widely consumed classes of antibiotics in the world and have high potential to resist degradation in the farmland soil. Thus, SA resistance genes(Suls) can easily be induced in the soil bacterium by SAs, and Suls have been commonly detected in farmland soils in the last decade. In the field of toxicology and pharmacology, it is well known that the activity of SAs can be significantly affected by it’s chemical structure characteristics, and the relationship between activity with structure has been extensively investigated and was named as quantitative structure and activity relationship(QSAR) model. It is, however, unclear that whether chemical structures of SAs can affect the inductive characteristics of Suls in SAs contaminated farmland soil, and how the mechanism for the corresponding relationship. Due to the large structural diverseness in commercial used SAs, answering these questions is the key to accurately evaluate the ecological risk of SAs and Suls in farmland soil. To address these questions, the test system of SAs contaminated red soil will be developed in this project and the following tests will be performed. Firstly, Suls concentrations, the relationship between Suls concentrations with time and SAs concentrations will be determined. Using calculated structural parameters of SAs, the relationship between SAs and inductive Suls concentration in SAs contaminated soil will be modeled on the basis of QSAR approach. Secondly, to further reveal the mechanisms for developed relationship, the SAs environmental behavior, the inductive of Suls in bacterial by SAs as well as the horizontal transfer characteristics of Suls will be investigated using the technology of chromatographic detection, fluorescent quantization and molecular simulation. Based on above results and using multivariate linear regression analysis, the mechanisms for the relationship between SAs and inductive Suls concentration in SAs contaminated soil will be developed from the viewpoint of antibiotic residue, gene expression and gene transfer, respectively. It is clear that the results of this project will be helpful to accurately evaluate the ecological hazard of SAs and Suls in the farmland soil.

磺胺类抗生素（SAs）及其抗性基因(Suls)是农田土壤典型污染物，且Suls主要是通过SAs诱导土壤细菌产生并传播的。研究表明，SAs化学结构可显著影响SAs活性并已在毒理等领域被广泛证实，但SAs化学结构如何影响SAs污染土壤中Suls的响应特征，土壤Suls响应水平与SAs间的构效关系以及形成该构效关系的机制是什么？尚不清楚。为此，本项目构建SAs污染的农田土壤，以Suls的生成与转移过程为主线，测定Suls对SAs污染的响应特征，计算SAs结构参数并构建结构活性定量相关模型，以探明Suls响应水平与SAs的构效关系。在此基础上，运用色谱、分子模拟及荧光定量等技术，研究SAs土壤残留差异及其成因、SAs对Suls生成的影响差异及成因、SAs对Suls转移的影响差异及成因，揭示土壤Suls对SAs污染响应的构效关系机制。研究成果为准确评价农田土壤SAs及Suls的生态风险提供科学依据。

磺胺类抗生素（SAs）及其抗性基因(Suls)是农田土壤典型污染物，且Suls主要是通过SAs诱导土壤细菌产生并传播的。研究表明，SAs化学结构可显著影响SAs活性并已在毒理等领域被广泛证实，但SAs化学结构如何影响SAs污染土壤中Suls的响应特征，土壤Suls响应水平与SAs间的构效关系以及形成该构效关系的机制是什么？尚不清楚。为此，本项目构建SAs污染的农田土壤，以Suls的生成与转移过程为主线，测定Suls对SAs污染的响应特征。基于Suls随时间的变化特征曲线，首次构建了一个新参数（ΔAR）并采用QSAR模型进行验证。结果表明，构建的新参数可以用于准确定量评价土壤中ARGs随时间的消长特征，且可用于描述ARGs对不同种类抗生素的响应以及不同环境中ARGs对抗生素污染的响应特性。计算SAs结构参数并构建结构活性定量相关模型，Suls的消长主要与SAs的pKa、logKow、Ehomo和qH+结构参数相关。此外，探究了SAs在土壤中的环境行为，研究表明生物降解是SAs在红壤中消减中占主要贡献。为揭示SAs影响Suls消长的机制，测定了导致SAs抗性突变的关键基因（folP）的表达。结果表明，试验SAs可增加folP基因的表达，基于分子对接剖析了folP编码的蛋白二氢叶酸合成酶（DHPS）与SAs的结合方式，发现结合能存在差异。进一步地，基于新参数ΔAR构建了相关模型，发现生物有效性和促进整合转移相关的频率是导致土壤中Suls产生的主要原因。宏基因组测序结果表明，参与了磺胺类抗生素微生物降解的物种/功能主要包括Bradyrhizobium、Sphingomonas和Methyloferula，CAZy功能中的GT51、GH23和GT2，eggNOG功能中的S，KEGG功能中的 ko02024、ko02010、K01999和K03088；物种/功能共现网络结果表明，Suls可能与多种物种/功能相关，同时一种物种/功能也可能与多种Suls相关。研究成果为准确评价农田土壤SAs及Suls的生态风险提供科学依据。此外，课题组同时开展了典型固体废弃物生物炭及类石墨烯生物炭对SAs吸附的差异及其形成机制相关研究，这对于降低环境中抗生素的生态风险及人体健康效应均具有重要的科学意义和实践价值。