Institute of Organic Contaminant Control and Soil Remediation, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, China.
College of Economics and Management, Nanjing Agricultural University, Nanjing 210095, China.
Sci Total Environ. 2021 Apr 10;764:144436. doi: 10.1016/j.scitotenv.2020.144436. Epub 2020 Dec 24.
Root exudates could influence the bioavailability of polycyclic aromatic hydrocarbons (PAHs), provide nutrients for soil microorganisms, and affect PAH biodegradation. However, it remains unclear how a bacterial community and its PAH-degrading genes play crucial roles in PAH biodegradation and respond to root exudates. In this study, a 32-day soil microcosm study was conducted to explore the impacts of artificial and actual root exudates on PAH degradation, degrading genes, and bacterial community structure. The results showed that 10-100 mg DOC/kg artificial and actual root exudates promoted the degradation of naphthalene, phenanthrene, and pyrene in soils, and their percent removal increased initially and then decreased with the increasing root exudates. Quantitative polymerase chain reaction analysis and 16S rRNA gene high-throughput sequencing suggested that the artificial root exudates significantly promoted the Nocardioides and Arthrobacter genera, which may harbor the nidA gene (the representative PAH-degrading gene from Gram-positive bacteria). In contrast, actual root exudates significantly stimulated the Pseudomonas genus that may harbor the nahAc gene (the representative PAH-degrading gene from Gram-negative bacteria). The correlation analysis further indicated that the absolute abundance of PAH degraders and degrading genes had strong correlations with PAH degradation efficiency. Therefore, these findings suggest that root exudates enhanced PAH biodegradation probably due to increases in abundance of both PAH-degraders and their degrading genes.
根系分泌物可能会影响多环芳烃（PAHs）的生物可利用性，为土壤微生物提供养分，并影响 PAH 的生物降解。然而，目前尚不清楚细菌群落及其 PAH 降解基因在 PAH 生物降解中如何发挥关键作用，以及它们如何对根系分泌物做出响应。在这项研究中，进行了为期 32 天的土壤微宇宙研究，以探索人工和实际根系分泌物对 PAH 降解、降解基因和细菌群落结构的影响。结果表明，10-100mg DOC/kg 的人工和实际根系分泌物促进了土壤中萘、菲和芘的降解，其去除率最初增加，然后随着根系分泌物的增加而降低。定量聚合酶链反应分析和 16S rRNA 基因高通量测序表明，人工根系分泌物显著促进了节杆菌属和节杆菌属的生长，这些菌可能含有 nidA 基因（革兰氏阳性菌中代表性的 PAH 降解基因）。相比之下，实际根系分泌物显著刺激了假单胞菌属的生长，该菌可能含有 nahAc 基因（革兰氏阴性菌中代表性的 PAH 降解基因）。相关性分析进一步表明，PAH 降解菌和降解基因的绝对丰度与 PAH 降解效率具有很强的相关性。因此，这些发现表明，根系分泌物增强了 PAH 的生物降解，可能是由于 PAH 降解菌及其降解基因的丰度增加所致。
