Bacterial degradation of 2,4-dinitrotoluene

MONTI MARIELA R.; SMANIA ANDREA M.; ARGARAÑA CARLOS E.

Tucumán, Argentina

Simposio; Simposio Internacional de Biotecnología, II Simposio Argentino-Italiano de Bacterias Lácticas.; 2004

The psychrophilic and fungal controlling rhizobacteria Pseudomonas fluorescens ATCC 17400 (PF17400) was engineered for degradation of the priority pollutant 2,4-dinitrotoluene (2,4-DNT). Firstly, a recombinant PF17400 was constructed by conjugative transfer of the pJS1 megaplasmid from Burkholderia sp strain DNT (BDNT) which contains the dnt genes for 2,4-DNT degradation. The heterologous expresión of dnt genes in PF17400 was confirmed by the ability of the recombinant strain to grow on 2,4-DNT as the sole source of carbon, nitrogen, and energy at equivalent levels as BDNT. Nevertheless, after extensive subcultures in 2,4-DNT free medium, loss of the 2,4-DNT degradative phenotype was observed from both pJS1-carrying PF17400 and BDNT. Subsequently, a stable degrading strain was generated by the transference of dntA, dntB and lower operon catabolic genes into the PF17400 chromosome. Although this new recombinant strain completely degraded 2,4-DNT and was capable of growing in liquid cultures with 2,4-DNT as a sole nitrogen source, it did not utilize this compound as a sole carbon and energy source. However, when this recombinant strain was grown on distinctive co-substrates, a more efficient 2,4-DNT degradation was observed. The present investigation reveals interesting insights about the transfer of the 2,4-DNT-degrading capacity into other bacterial species such as the environmental robust PF17400 that would be helpful to the development of new recombinant bacteria adapted to specific ecosystems for the design of bioremediation strategies in particular environments