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Biodegradation of Mixed PAHs by PAH-Degrading Endophytic Bacteria

Institute of Organic Contaminant Control and Soil Remediation, College of Resource and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, China
Author to whom correspondence should be addressed.
Academic Editor: Miriam C. Poirier
Int. J. Environ. Res. Public Health 2016, 13(8), 805;
Received: 28 June 2016 / Revised: 26 July 2016 / Accepted: 3 August 2016 / Published: 9 August 2016
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Endophytic bacteria can promote plant growth, induce plant defence mechanisms, and increase plant resistance to organic contaminants. The aims of the present study were to isolate highly PAH-degrading endophytic bacteria from plants growing at PAH-contaminated sites and to evaluate the capabilities of these bacteria to degrade polycyclic aromatic hydrocarbons (PAHs) in vitro, which will be beneficial for re-colonizing target plants and reducing plant PAH residues through the inoculation of plants with endophytic bacteria. Two endophytic bacterial strains P1 (Stenotrophomonas sp.) and P3 (Pseudomonas sp.), which degraded more than 90% of phenanthrene (PHE) within 7 days, were isolated from Conyza canadensis and Trifolium pretense L., respectively. Both strains could use naphthalene (NAP), PHE, fluorene (FLR), pyrene (PYR), and benzo(a)pyrene (B(a)P) as the sole sources of carbon and energy. Moreover, these bacteria reduced the contamination of mixed PAHs at high levels after inoculation for 7 days; strain P1 degraded 98.0% NAP, 83.1% FLR, 87.8% PHE, 14.4% PYR, and 1.6% B(a)P, and strain P3 degraded 95.3% NAP, 87.9% FLR, 90.4% PHE, 6.9% PYR, and negligible B(a)P. Notably, the biodegradation of PAHs could be promoted through additional carbon and nitrogen nutrients; therein, beef extract was suggested as the optimal co-substrate for the degradation of PAHs by these two strains (99.1% PHE was degraded within 7 days). Compared with strain P1, strain P3 has more potential for the use in the removal of PAHs from plant tissues. These results provide a novel perspective in the reduction of plant PAH residues in PAH-contaminated sites through inoculating plants with highly PAH-degrading endophytic bacteria. View Full-Text
Keywords: endophytic bacteria; Pseudomonas sp.; Stenotrophomonas sp.; 16S rRNA gene; biodegradation endophytic bacteria; Pseudomonas sp.; Stenotrophomonas sp.; 16S rRNA gene; biodegradation

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Zhu, X.; Ni, X.; Waigi, M.G.; Liu, J.; Sun, K.; Gao, Y. Biodegradation of Mixed PAHs by PAH-Degrading Endophytic Bacteria. Int. J. Environ. Res. Public Health 2016, 13, 805.

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