四环素抗性基因（TRGs）威胁人类健康已成为全球关注的热点问题。我们发现土壤TRGs丰度受不同形态氮素影响，不同形态氮素又影响tetR表达水平，据此提出“因调节基因tetR受氮素形态影响，相比有机氮主导的或单一氮源肥料，复合无机氮素主导的肥料对土壤TRGs积累风险较小”假说。本申请项目首先考察四环素抗性菌株混合培养物的TRGs和tetR丰度对不同形态氮素的响应规律；阐明不同形态氮素对不同土壤TRGs的影响；利用RT-qPCR技术明确对不同形态氮素发生响应的TRGs和tetR的表达情况，综合基因和转录水平实验结果，揭示tetR受不同形态氮素诱导以调控TRGs表达，并最终影响TRGs在土壤中积累的分子机制；通过田间试验，探索有机/无机氮肥的合理混施模式；构建TetR高表达菌株用于TRGs防控。研究有望揭示不同氮肥施用模式对土壤TRGs积累的规律及机制，为TRGs防控提供理论认知与技术支撑。

The increasing threat of tetracycline resistance genes (TRGs) to people’s health is becoming a hot issue. We found that the accumulation of TRGs was affected by different forms of nitrogen, which is also probably related to the expression of tetR. Based on this, we advance a hypothesis that due to the regulatory gene tetR is affected by nitrogen forms; the combined inorganic nitrogen-dominated fertilizers have less risk of soil TRGs accumulation compared with the organic nitrogen-dominated fertilizers or single-source fertilizers. In this project, we will first investigate the effect of different forms of nitrogen on the abundances of TRGs and tetR in the mixed culture of tetracycline-resistant bacteria stored in our lab. Next, the effect of different forms of nitrogen on TRGs abundances in different kinds of soil will be studied. Thirdly, the expressions of TRGs and tetR will be determined using RT-qPCR, which combined with the results above may uncover the mechanism of accumulation of tetracycline resistance genes in soil via regulatory gene tetR induced by different forms of nitrogen. Fourthly, the reasonable fertilization mode with of organic/inorganic fertilizers will be advanced through field experiments. Finally, a novel method for TRGs controlling will be presented by application of a mutant strain with high expression of tetR. This study can illustrate the mechanism of accumulation of tetracycline resistance genes in soil via regulatory gene tetR induced by different forms of nitrogen, and also offer theoretical perspective and technical support for the TRGs controlling.