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| Determining the effects of Serratia sp. PW7 on pyrene removal and the endophytic bacterial community in ryegrass (Lolium multiflorum L.)via different inoculation methods |
| Received:December 26, 2017 |
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| KeyWord:pyrene;functional endophytic bacteria;inoculation;endophytic bacterial community |
| Author Name | Affiliation | E-mail | | LI Shuang | College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, China | | | ZUO Shang-wu | College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, China | | | WANG Wan-qing | Tianjin College, University of Science & Technology Beijing, Tianjin 301830, China | | | WANG Jin-song | College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, China | | | QUAN Cheng-wei | College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, China | | | ZHU Xue-zhu | College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, China | zhuxuezhu@njau.edu.cn |
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| Abstract: |
| To understand the mechanism by which PAHs (polycyclic aromatic hydrocarbons) are removed from plants by functional endophytic bacteria, pyrene residues and cultivable endophytic bacterial communities in a ryegrass plant inoculated with Serratia sp. strain PW7 were investigated. The results showed that the PW7 strain of Serratia sp. could efficiently colonize in the roots (5.87~7.63 lg CFU·g-1) and shoots (3.49~4.97 lg CFU·g-1) of the inoculated seedlings. Colonization by PW7 strain significantly increased pyrene removal, plant growth, and the cell counts and diversities of cultivable endophytic bacteria. Remarkably, pyrene removal efficiency and plant growth were both positively correlated with the establishment efficiency of PW7 strain. Compared to the seedlings inoculated by soaking the seeds, more cells of the PW7 strain successfully colonized in the seedlings inoculated by dipping the roots, leading to less pyrene residues. Inoculated by dipping the roots enhanced the growth of inoculated seedlings by 18.5%~28.0% and decreased the pyrene concentation by 35.7%~44.2%. Meanwhile, the maximal indices of diversity and evenness (H=2.22, J=0.865) were found in the roots of the seedlings from group LR grown in Hoagland solution with 0.5 mg·L-1 pyrene. The endophytic bacterial population could be shifted by PW7 strain as the seedlings were exposed to pyrene. For the seedlings grown in the Hoagland solution with pyrene, the most dominant bacteria was Serratia, and the other dominant bacteria were Pantoea, Erwinia, and Micrococcus in the roots of inoculated seedlings. Whereas, in the shoots of inoculated seedlings grown in the Hoagland solution with pyrene, the most dominant bacteria remained Microbacterium, and other dominant bacteria shifted from Chryseobacterium to Pantoea, Pseudomonas, and Sphingobacterium. Moreover, seven strains of these dominant bacteria could degrade more than 55% of the pyrene in the media within 15 d. Our results clarified that functional endophytic PW7 strain could effectively increase the pyrene removal efficiency by increasing endophytic bacterial diversities and shifting the dominant endophytic bacteria. |
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