Degradation of 2,4,6-Trinitrotoluene (TNT): Involvement of Protocatechuate 3,4-Dioxygenase (P34O) in Buttiauxella sp. S19-1

Abstract

Extensive use and disposal of 2,4,6-trinitrotoluene (TNT), a primary constituent of explosives, pollutes the environment and causes severe damage to human health. Complete mineralization of TNT via bacterial degradation has recently gained research interest as an effective method for the restoration of contaminated sites. Here, screening for TNT degradation by six selected bacteria revealed that Buttiauxella sp. S19-1, possesses the strongest degrading ability. Moreover, BuP34O (a gene encoding for protocatechuate 3,4-dioxygenase—P34O, a key enzyme in the β-ketoadipate pathway) was upregulated during TNT degradation. A knockout of BuP34O in S19-1 to generate S-M1 mutant strain caused a marked reduction in TNT degradation efficiency compared to S19-1. Additionally, the EM1 mutant strain (Escherichia coli DH5α transfected with BuP34O) showed higher degradation efficiency than DH5α. Gas chromatography mass spectrometry (GC-MS) analysis of TNT degradation by S19-1 revealed 4-amino-2,6-dinitrotolune (ADNT) as the intermediate metabolite of TNT. Furthermore, the recombinant protein P34O (rP34O) expressed the activity of 2.46 µmol/min·mg. Our findings present the first report on the involvement of P34O in bacterial degradation of TNT and its metabolites, suggesting that P34O could catalyze downstream reactions in the TNT degradation pathway. In addition, the TNT-degrading ability of S19-1, a Gram-negative marine-derived bacterium, presents enormous potential for restoration of TNT-contaminated seas.

Comparative Genomic Analysis of Antarctic Pseudomonas Isolates with 2,4,6-Trinitrotoluene Transformation Capabilities Reveals Their Unique Features for Xenobiotics Degradation

“…As demonstrated for the first time by a recent knockout study on a deletion mutant for this gene in Buttiauxella sp. S19-1, the P3,4O enzyme is involved in the degradation of TNT and its metabolites, possibly catalyzing downstream reactions in this pathway [ 11 ]. It is worth emphasizing that the genes encoding P3,4O in both TNT3 and TNT19 share sequence identity below 50% when compared to that of P. putida strains KT2440 and JLR11.…”

“…Since it has been recently reported that the protocatechuate 3,4-dioxygenase (P3,4O) enzyme of the β-ketoadipate pathway increases the degradation of TNT and 4ADNT in Buttiauxella sp. S19-1 [ 11 ], we propose that the P3,4O enzyme and other enzymes of the β-ketoadipate pathway (encoded by unique genes as mentioned earlier) could also participate in TNT transformation on TNT isolates. In Figure 6 a, green arrows indicate that TNT-degrading enzymes (e.g., nitroreductases, OYEs, etc.)…”

“…In contrast, bioremediation, a biological approach to remove toxic waste by using biological agents such as microorganisms, offers advantages to achieve complete transformation or mineralization of TNT in an environmentally friendly manner [ 3 ]. However, the development of effective treatments and strategies for complete onsite clean-up and detoxification of this compound is an issue that remains unsolved and has regained research interest in recent years [ 8 , 9 , 10 , 11 ].…”

Changes in the Bacillus pumilus proteome during 2,4,6-trinitrotoluene degradation

“…revealed the downregulation of 36 and 48 genes, and upregulation of 72 and 63 genes during the 6 and 12 hours of incubation, respectively. Among upregulated genes are aldehyde dehydrogenase and monooxygenase, which are key enzymes of the TNT degradation pathway (Xu et al 2021). In our study, oxidoreductases like the FMN-dependent NADHazoreductase and nitrate reductase were also upregulated.…”

Recruiting Perovskites to Degrade Toxic Trinitrotoluene

“…Typically, energetic materials are discarded through open burning/open detonation, or in landfills. Although many disposal technologies (including activated carbon adsorption [ 36 , 37 , 38 ], photocatalysis [ 39 , 40 , 41 ], oxidation [ 42 , 43 ], biodegradation [ 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 ], hydrothermal processing [ 52 ], and electric discharge [ 53 ] etc.) are being explored, no reliable, safe, environmentally sound, and cost-efficient means of disposal are available yet [ 47 , 48 , 54 ].…”