Endophytic Burkholderia fungorum DBT1 can improve phytoremediation efficiency of polycyclic aromatic hydrocarbons

Burkholderia fungorum DBT1 is a bacterial strain isolated from an oil refinery discharge and capable of transforming dibenzothiophene, phenanthrene, naphthalene, and fluorene. In order to evaluate the influence of a policyclic aromatic hydrocarbon (PAH)-transforming bacterial strain on the phytoremediation of organic contaminants, B. fungorum DBT1 was inoculated into hybrid poplar (Populus deltoides x Populus nigra). The poplar plants were grown for 18-wk with or without naphthalene, phenanthrene, fluorene and dibenzothiophene (488 mg kg(-1) soil each) in non-sterile sand-peat substrate. Evidences were gained that B. fungorum DBT1 was present in high concentration in poplar root tissues (2.9-9.5 x 10(3) CFU g(-1)), while the strain was not detected in stem, leaves and rhizosphere. When poplar was planted in uncontaminated substrate, the infection caused negative effects on biomass index, leaves and stem dry weight, without showing however any disease symptoms. On the other hand, plants inoculated with the strain DBT1 resulted in better tolerance against the toxic effects of PAHs, in terms of root dry weight. Although the presence of plants acted as the main effective treatment for PAH dissipation (82-87%), the inoculum with DBT1 strain lead to the highest PAH abatement (up to 99%). In the present study, an environmental isolate with proper metabolic features was demonstrated to be possibly suitable as a poplar endophyte for improving microbe-assisted phytoremediation in PAH contaminated matrices. (c) 2013 Elsevier Ltd. All rights reserved.