根系分泌物对土壤中多环芳烃降解及相关微生物的影响

Effects of Root Exudates on Degradation of Polycyclic Aromatic Hydrocarbons and Related Microorganisms in Soil

根系分泌物可有效降解有机污染物,目前尚不清楚根系分泌物对土壤中多环芳烃(PAH)降解效果、降解基因及相关功能菌丰度的影响。本研究采用盆栽试验,探索不同浓度(10、20、40、80 mg/kg)人工根系分泌物、水稻根系分泌物对PAH(NAP、PHE、PYR)降解率、降解基因(nidA、nahAc、phe)丰度和细菌群落结构的影响。结果表明,添加10~80 mg/kg的人工和水稻根系分泌物处理皆可在一定程度提高土壤中NAP、PHE、PYR的降解率,且降解率随着根系分泌物浓度的增加呈先增加后降低趋势,整体以40 mg/kg效果较佳。qRT-PCR和16S rRNA高通量测序表明,与CK处理相比,根系分泌物处理下微生物群落丰度发生明显变化,且不同时间、不同浓度皆可影响群落结构特征。相关性分析结果表明,PAH降解效率、降解基因丰度、PAH功能菌三者间皆具有很强的相关性;人工根系分泌物处理下PAH降解率与nidA基因、诺卡氏菌属(Nocardioides)和分枝杆菌属(Mycobacterium)呈极显著正相关(P<0.01),水稻根系分泌物处理下PAH降解率与nahAc基因、假单胞菌属(Pseudomonas)呈极显著正相关。综上,人工根系分泌物及水稻根系分泌物皆可促进土壤中PAH的生物降解。

Root exudates can effectively degrade organic pollutants, but the effects of root exudates on degradation of polycyclic aromatic hydrocarbons(PAHs) in soil, abundance of degradation genes and related functional bacteria were still unclear. In this study, pot experiment was used to explore the effects of artificial root exudates and rice root exudates at different concentrations(10, 20, 40, 80 mg/kg) on degradation rates of PAHs(NAP, PHE, PYR), abundance of degradation genes(nidA, nahAc, phe) and bacterial community structure. The results showed that the addition of 10~80 mg/kg artificial and rice root exudates could increase the degradation rates of NAP, PHE and PYR in soil to a certain extent, and the degradation rates first increased and then decreased with the increase of root exudates concentration. The overall effect was better at 40 mg/kg. qRT-PCR and 16 S rRNA high-throughput sequencing results showed that compared with CK treatment, the microbial community abundance changed significantly under the root exudate treatment, and different time and concentrations could affect the community structure characteristics. Correlation analysis further showed that PAH degradation efficiency, degradation gene abundance and PAH functional bacteria had strong correlations;PAH degradation efficiency under artificial root exudates treatment had significant(P<0.01) positive correlation with nidA gene, Nocardioides and Mycobacterium, the PAH degradation rate under the rice root exudates treatment had significant positive correlation with nahAc gene and Pseudomonas. In conclusion, both artificial root exudates and rice root exudates could improve the biodegradation of PAH.