We previously reported the construction of a recombinant Pseudomonas fluorescens strain for degradation of 2,4-dinitrotoluene (2,4-DNT). This strain, named RE, was obtained by the chromosomal insertion of the dnt catabolic genes from the megaplasmids present in Burkholderia DNT and R34 strains. We here analyze different features of the recombinant strain relevant for its potential application in bioremediation processes. It is shown that, in contrast to the plasmid borne Burkholderia DNT, P. fluorescens RE presents a long-stable degradative phenotype. Moreover, the recombinant strain was capable of completely degrading 2,4-DNT at low temperatures whereas Burkholderia DNT was inefficient in the same conditions. P. fluorescens RE was also able to counteract 2,4-DNT toxicity on Nicotiana tabacum and Arabidopsis thaliana development in synthetic medium containing the nitroaromatic compound. Interestingly, P. fluorescens RE was found to be non- toxic for A. thaliana and Nicotiana tabacum, whereas Burkholderia DNT inhibited A. thaliana seed germination and produced plant lethality in such in vitro assays. Finally, the presence of P. fluorescens RE in soil microcosms containing plant lethal levels of 2,4-DNT significantly decreased the toxic effects of this nitrocompound on A. thaliana growth. These results reveal the advantages of P. fluorescens RE and reinforce its potentiality as vehicle for the cleaning up of 2,4-DNT contaminated environments.
