Nicotiana tabacum-associated bioengineered Pseudomonas putida can enhance rhizoremediation of soil containing 2,4-dinitrotoluene

Abstract

Rhizoremediation processes are based on plant-bacteria interactions and can be effectively used for cleaning many pollutants from the environment to overcome the constraints of individual phytoremediation. Here, 1 mM and 1.5 mM concentrations of 2,4-dinitrotoluene (2,4-DNT) degrading Pseudomonas putida (P. putida) strain KT.DNT and various growth stages of Nicotiana tabacum (N. tabacum) were initially assayed in in vitro tissue culture system and the best conditions for the association of plant-rhizobacterium were ascertained to remediation of the soil contaminated with 2,4-DNT. 5-days old N. tabacum plants inoculated with 2x10(6) cfu/mL bacterial inoculum for 3 weeks were preferred for rhizoremediation experiments as they showed a nearly threefold increase in the fresh and dry biomass in comparison to noninoculated ones. When these seedlings were planted either alone or together with P. putida KT2440 or P. putida KT.DNT in soils contaminated with 1 mM and 1.5 mM of 2,4-DNT, the maximum degradation rate of 98% and similar to 93% were determined at the end of 14 days by KT.DNT inoculated tobacco plants. Our results indicate that it would be advantageous to use the 2,4-DNT-degrading bacterium inoculated with N. tabacum plants to accelerate and enhance the cleanup of soil contaminated with 2,4-DNT.