Efficacy of ornamental plants for benzene removal from contaminated air and water: Effect of plant associated bacteria

• C. comosum showed the highest benzene removal efficiency.
• Removal rate of benzene by non-sterilized plants was higher than sterilized plants.
• Enterobacter EN2, a high benzene tolerant bacteria, was colonized in inoculated plants.
• C. comosum-endophyte Enterobacter EN2 interactions enhanced benzene removal.

In the present study, eight plant species – Syngonium podophyllum, Sansevieria trifasciata, Euphorbia milii, Chlorophytum comosum, Epipremnum aureum, Dracaena sanderiana, Hedera helix, and Clitoria ternatea were exposed to benzene under hydroponic conditions to evaluate the benzene uptake rates. Among the tested plants, C. comosum showed the highest benzene removal efficiency. However, the results indicated that the removal rates of non-sterilized plants were higher than that of sterilized plants. This variation was due to the different responses of plant associated bacteria. Benzene-resistant bacteria of C. comosum were isolated and characterized. Of the 14 isolated bacteria, results showed that 5 isolates are endophytic bacteria, while 9 isolates are epiphytic bacteria. It was revealed that 1 isolate of endophytic bacteria (EN2), and 2 isolates of epiphytic bacteria (EPL1 and EPR2) had the highest benzene removal efficiencies. These species were identified and designated by 16S rDNA as Enterobacter EN2, Cronobacter EPL1, and Pseudomonas EPR2. Enterobacter EN2 strain efficiently colonized the inoculated plants. A high rate of IAA production and benzene tolerance was found in the plants inoculated with this strain. These findings further elucidated that plant associated bacteria play essential roles in removing benzene from the contaminated system.