Abstract：
Rhizoremediation and bioaugmentation have proven effective in promoting benzo[a]pyrene (BaP) degradation in contaminated soils. However, the mechanism underlying bioaugmented rhizospheric BaP degradation with native microbes is poorly understood. In this study, an indigenous BaP degrader (Stenotrophomonas BaP-1) isolated from petroleum-contaminated soil was introduced into ryegrass rhizosphere to investigate the relationship between indigenous degraders and rhizospheric BaP degradation. Stable isotope probing and 16S rRNA gene amplicon sequencing subsequently revealed 15 BaP degraders, 8 of which were directly associated with BaP degradation including Bradyrhizobium and Streptomyces. Bioaugmentation with strain BaP-1 significantly enhanced rhizospheric BaP degradation and shaped the microbial community structure. A correlation of BaP degraders, BaP degradation efficiency, and functional genes identified active degraders and genes encoding polycyclic aromatic hydrocarbon-ring hydroxylating dioxygenase (PAH-RHD) genes as the primary drivers of rhizospheric BaP degradation. Furthermore, strain BaP-1 was shown to not only engage in BaP metabolism but also to increase the abundance of other BaP degraders and PAH-RHD genes, resulting in enhanced rhizospheric BaP degradation. Metagenomic and correlation analyses indicated a significant positive relationship between glyoxylate and dicarboxylate metabolism and BaP degradation, suggesting a role for these pathways in rhizospheric BaP biodegradation. By identifying BaP degraders and characterizing their metabolic characteristics within intricate microbial communities, our study offers valuable insights into the mechanisms of bioaugmented rhizoremediation with indigenous bacteria for high-molecular-weight PAHs in petroleum-contaminated soils.
摘要：
根治和生物强化已被证明可有效促进污染土壤中的苯并[a]芘（BaP）降解。然而,对天然微生物的生物增强根际BaP降解的潜在机制知之甚少。在这项研究中,从石油污染的土壤中分离出的一种本土BaP降解剂（StenotrophonomasBaP-1）被引入黑麦草根际，以研究本土降解剂与根际BaP降解之间的关系。稳定的同位素探测和16SrRNA基因扩增子测序随后揭示了15个BaP降解物，其中8个与BaP降解直接相关，包括缓生根瘤菌和链霉菌。菌株BaP-1的生物强化显着增强了根际BaP的降解并塑造了微生物群落结构。BaP降解剂的相关性，BaP降解效率,和功能基因确定了活性降解剂和编码多环芳烃环羟基化双加氧酶（PAH-RHD）基因的基因是根际BaP降解的主要驱动因素。此外，菌株BaP-1不仅参与BaP代谢，而且还增加其他BaP降解物和PAH-RHD基因的丰度，导致根际BaP降解增强。宏基因组和相关分析表明乙醛酸和二羧酸代谢与BaP降解之间存在显着的正相关关系，表明这些途径在根际BaP生物降解中的作用。通过鉴定BaP降解剂并在复杂的微生物群落中表征其代谢特征，我们的研究为石油污染土壤中使用本地细菌对高分子量PAHs进行生物增强根治的机制提供了宝贵的见解。
