汽车拆解场地污泥微生物对磷酸三(1-氯-2-丙基)酯的厌氧转化

Anaerobic biotransformation of tris(1-chloro-2-propyl) phosphate by an enrichment culture from vehicle dismantling site sludge

摘要:

【背景】 磷酸三(1-氯-2-丙基)酯[tris (1-chloro-2-propyl) phosphate, TCPP]作为一种添加型有机磷酸酯阻燃剂，被广泛应用于汽车内饰、电子电器及家具等领域。随着全球汽车报废量的快速增长，汽车拆解场地已成为TCPP污染的重要热点区域。目前，关于TCPP在拆解场地复杂环境中的微生物转化过程及其驱动机制仍不明确。前期研究表明，有机卤呼吸细菌(organohalide-respiring bacteria, OHRB)可能通过还原脱卤作用参与TCPP的厌氧生物转化，但其中关键功能酶——还原脱卤酶对TCPP的催化机制及其编码基因尚未得到解析。【目的】 揭示汽车拆解场地微生物对TCPP的厌氧转化途径与分子机制，鉴定其中的关键功能微生物类群，阐明OHRB中参与TCPP转化的还原脱卤酶基因rdhA及其转录特征。【方法】 从汽车拆解场地污泥中富集了一个高效转化TCPP的含脱卤拟球菌属(Dehalococcoides)的厌氧菌群；采用高分辨液相色谱-质谱鉴定TCPP转化产物；结合高通量测序、宏基因组分箱、逆转录-定量PCR技术，鉴定参与TCPP转化的关键功能微生物和功能基因。【结果】 识别出TCPP的5种转化产物，其中丙烯和磷酸二(1-氯-2-丙基)酯[bis (1-chloro-2-propyl) phosphate, BCPP]是主要转化产物。Dehalococcoides含有8个rdhA基因，其中一个rdhA基因(命名为perA基因)在TCPP胁迫下转录水平显著上调。【结论】 证实了汽车拆解场地污泥微生物对TCPP的厌氧转化潜力，识别出5种转化产物，推断TCPP可能主要通过断裂C−Cl键和C−O键的途径转化为BCPP和丙烯。Dehalococcoides的perA基因可能在TCPP的脱氯转化过程中发挥关键作用。研究结果不仅深化了对氯代有机磷酸酯环境行为机理的认识，也为TCPP污染场地的生物修复提供了理论依据。

Abstract:

[Background] Tris(1-chloro-2-propyl) phosphate (TCPP), a widely used additive organophosphate flame retardant, is extensively applied in vehicle interiors, electronic appliances, and household furniture. With the rapid increase in global end-of-life vehicles, vehicle dismantling sites have become significant hotspots of TCPP contamination. However, the microbial transformation processes and mechanisms of TCPP in such complex environments remain unclear. Previous studies suggested that organohalide-respiring bacteria (OHRB) may participate in the anaerobic biotransformation of TCPP via reductive dehalogenation, while the catalytic mechanism of reductive dehalogenase and its coding gene have not been identified. [Objective] To reveal the pathways and molecular mechanisms underpinning the anaerobic transformation of TCPP by a microbial culture enriched from a vehicle dismantling site, identify the key functional microorganisms, and characterize the reductive dehalogenase (rdhA) genes involved in TCPP transformation. [Methods] An anaerobic microbial culture capable of efficiently transforming TCPP was enriched from sludge of a vehicle dismantling site. Transformation products were identified by high-resolution LC-MS. Key functional microorganisms and genes involved in TCPP transformation were identified by high-throughput sequencing, metagenomic binning and RT-qPCR. [Results] Five TCPP transformation products were identified, with propene and bis(1-chloro-2-propyl) phosphate (BCPP) being the primary transformation products. The genome of Dehalococcoides contained eight rdhA genes, among which one rdhA gene, designated perA, showed significantly upregulated transcription with TCPP amendment. [Conclusion] This study confirmed the anaerobic transformation potential of sludge microorganisms from a vehicle dismantling site toward TCPP, identified five transformation products, and proposed that TCPP was mainly transformed into propene and BCPP via a dechlorination pathway involving the cleavage of C−Cl and C−O bonds. The perA gene in Dehalococcoides might play a critical role in the dechlorination of TCPP. The findings enhance the understanding of the environmental behavior mechanisms of chlorinated organophosphate esters and provide a theoretical basis for the bioremediation of TCPP-contaminated sites.