Biological degradation of 2,4,6-Trinitrotoluene (TNT) : bioprospecting for TNT-denitrating bacteria and deciphering of multiple TNT denitration pathways
(2009)
Files
Stenuit.pdf
Restricted Access - Adobe PDF
- 115.9 MB
Details
- Authors
- Supervisors
- Agathos, Spyridon
- Abstract
- 2,4,6-Trinitrotoluene (TNT), historically the most widely used explosive, is recalcitrant to biodegradation. Its toxicity and the relatively high extent of pollution have raised our attention to the imperative of providing sustainable remediation technologies, making the development of efficient biocatalysts crucial. Here bioprospecting on a TNT-contaminated soil (called KX1) was carried out to discover new TNT denitration catalysts that can lead to denitrated metabolites prone to oxidative biodegradation. The first aim of this study focused on the culture-independent analysis of its entire catabolic potential via the function-driven screening of a metagenomic library constructed from KX1. However, even negative results of screening a metagenomic library because of an ill-adapted host organism can be valuable, as illustrated by our discovery of a strong TNT denitration capacity in Escherichia coli. The second was to monitor anoxic enrichment cultures inoculated with KX1 soil samples and spiked with TNT as the sole N source, which led to the isolation of the TNT-denitrating bacterium Pseudomonas aeruginosa ESA-5. The (bio)chemistry of TNT biodegradation pathways catalyzed by E. coli and P. aeruginosa was then investigated. Two dissimilar NADP(H)-dependent TNT denitration pathways have been detected involving a distinct nucleophilic attack of the electron-deficient aromatic ring of TNT. Heterologous expression of nemA of E. coli and xenPA of P. aeruginosa, encoding two members of the Old Yellow Enzyme family of flavoproteins, demonstrated the nucleophilic attack of TNT by hydride ions followed by its denitration. Finally, the redox-active metabolite pyocyanin secreted by P. aeruginosa was characterized and shown to promote TNT denitration through the nucleophilic attack of TNT by superoxide ions generated by a biomimetic system (NAD(P)H/PYO).
- Affiliations
Citations
Sténuit, B. (2009). Biological degradation of 2,4,6-Trinitrotoluene (TNT) : bioprospecting for TNT-denitrating bacteria and deciphering of multiple TNT denitration pathways. https://hdl.handle.net/2078.5/124047