三叶草根系分泌物对多环芳烃微生物降解及加氧酶的影响

Effects of root exudates of clover (Trifolium repens) on PAH microbial degradation and dioxygenase

为揭示根际效应对多环芳烃降解的影响机制,建立恰当的植物-微生物联合修复模式,本研究向含有微生物及多环芳烃(芘和苯并[a]芘)的微宇宙中加入三叶草根系分泌物,分析其对多环芳烃降解的影响,研究降解过程中微生物加氧酶和16S rDNA基因拷贝数的变化,并对具有多环芳烃降解能力的微生物进行鉴定.结果表明:分枝杆菌M1具有降解多环芳烃的能力;三叶草根系分泌物总有机碳(TOC)浓度为35.5 mg·L-1时,芘和苯并[a]芘降解率明显提高,分枝杆菌加氧酶基因所占比例增加,表明其促进了分枝杆菌对芘和苯并[a]芘的降解;在降解过程中,加氧酶基因拷贝数明显增加,而16S rDNA数量增加不明显,表明前者与多环芳烃降解过程有关,而后者和微生物数量有关.三叶草根系分泌物使分枝杆菌加氧酶基因拷贝数明显增加,从而促进了分枝杆菌对多环芳烃的降解.

To demonstrate rhizospheric effect on the mechanism of （polycyelic aromatic hydrocarbon） PAH degradation, and to establish a proper joint phyto-microbial remediation mode, microcosms containing microorganisms and PAHs （pyrene and benzo [a] Pyrene） were added with clover （Trifolium repens） root exudates to study their effects on PAH degradation. Dioxygenase gene and 16S rDNA gene copy number changes during the biodegradation process were analyzed, and the microorganism with a good ability for degrading PAHs was identified. The results showed that Mycobacterium M1 had the capability to degrade PAHs. When total organic carbon （TOC） concentration of clover root exudates was 35.5 mg ·L^-1, pyrene and benzol [a] pyrene degradation rates increased significantly, and the proportion of dioxygenase gene to 165 rDNA of Mycobacterium M1 increased. In the biodegradation process, dioxygenase gene copy number increased significantly, whereas 16S rDNA copy number increase was not so obvious, showing that the former was related to degradation process, but the latter was related to microbial numbers. It was concluded that the clover root exudates promoted the dioxygenase gene copy number of Mycobacterium M1, which contributed to the degradation of PAHs.