Anhui Provincial Key Laboratory for Quality and Safety of Agri-Products, School of Resource & Environment, Anhui Agricultural University, Hefei, Anhui 230036, China.
Anhui Provincial Key Laboratory for Quality and Safety of Agri-Products, School of Resource & Environment, Anhui Agricultural University, Hefei, Anhui 230036, China; Institute for Green Development, Anhui Agricultural University, Hefei, Anhui 230036, China.
Sci Total Environ. 2024 Feb 20;912:168957. doi: 10.1016/j.scitotenv.2023.168957. Epub 2023 Nov 27.
Fungicide carboxin was commonly used in the form of seed coating for the prevention of smut, wheat rust and cotton damping-off, leading carboxin and its probable carcinogenic metabolite aniline to directly enter the soil with the seeds, causing residual pollution. In this study, a novel carboxin degrading strain, Delftia sp. HFL-1, was isolated. Strain HFL-1 could use carboxin as the carbon source for growth and completely degrade 50 mg/L carboxin and its metabolite aniline within 24 h. The optimal temperatures and pH for carboxin degrading by strain HFL-1 were 30 to 42 °C and 5 to 9, respectively. Furthermore, the complete mineralization pathway of carboxin by strain HFL-1 was revealed by High Resolution Mass Spectrometer (HRMS). Carboxin was firstly hydrolyzed into aniline and further metabolized into catechol through multiple oxidation processes, and finally converted into 4-hydroxy-2-oxopentanoate, a precursor of the tricarboxylic acid cycle. Genome sequencing revealed the corresponding degradation genes and cluster of carboxin. Among them, amidohydrolase and dioxygenase were key enzymes involved in the degradation of carboxin and aniline. The discovery of transposons indicated that the aniline degradation gene cluster in strain HFL-1 was obtained via horizontal transfer. Furthermore, the degradation genes were cloned and overexpressed. The in vitro test showed that the expressed degrading enzyme could efficiently degrade aniline. This study provides an efficient strain resource for the bioremediation of carboxin and aniline in contaminated soil, and further revealing the molecular mechanism of biodegradation of carboxin and aniline.
杀菌剂 carbozine 通常以种子包衣的形式用于预防黑穗病、小麦锈病和棉花猝倒病，导致 carbozine 和其可能的致癌代谢物苯胺随种子直接进入土壤，造成残留污染。本研究分离到一株新型 carbozine 降解菌 Delftia sp. HFL-1。该菌可以 carbozine 作为生长的碳源，在 24 h 内完全降解 50 mg/L 的 carbozine 和其代谢物苯胺。HFL-1 菌株降解 carbozine 的最适温度和 pH 值分别为 30 至 42°C 和 5 至 9。此外，通过高分辨质谱（HRMS）揭示了 HFL-1 菌株对 carbozine 的完全矿化途径。Carbozine 首先水解为苯胺，然后通过多次氧化过程进一步代谢为儿茶酚，最后转化为 4-羟基-2-氧戊酸，三羧酸循环的前体。基因组测序揭示了 carbozine 的相应降解基因和基因簇。其中，酰胺水解酶和双加氧酶是参与 carbozine 和苯胺降解的关键酶。转座子的发现表明，HFL-1 菌株中的苯胺降解基因簇是通过水平转移获得的。进一步克隆和过表达降解基因。体外试验表明，表达的降解酶能有效降解苯胺。本研究为污染土壤中 carbozine 和苯胺的生物修复提供了高效的菌株资源，进一步揭示了 carbozine 和苯胺生物降解的分子机制。
