Biotransformation of explosives by the old yellow enzyme family of flavoproteins

Several independent studies of bacterial degradation of nitrate ester explosives have demonstrated the involvement of flavin-dependent oxidoreductases related to the old yellow enzyme (OYE) of yeast. Some of these enzymes also transform the nitroaromatic explosive 2,4,6-trinitrotoluene (TNT). In this work, catalytic capabilities of five members of the OYE family were compared, with a view to correlating structure and function. The activity profiles of the five enzymes differed substantially; no one compound proved to be a good substrate for all five enzymes. TNT is reduced, albeit slowly, by all five enzymes. The nature of the transformation products differed, with three of the five enzymes yielding products indicative of reduction of the aromatic ring. Our findings suggest two distinct pathways of TNT transformation, with the initial reduction of TNT being the key point of difference between the enzymes. Characterization of an active site mutant of one of the enzymes suggests a structural basis for this difference

The highly conserved Escherichia coli transcription factor YhaJ regulates aromatic compound degradation

The aromatic compound 2,4-dinitrotoluene (DNT), a common impurity in 2,4,6-trinitrotoluene (TNT) production, has been suggested as a tracer for the presence of TNT-based landmines due to its stability and high volatility. We have previously described an Escherichia coli bioreporter capable of detecting the presence of DNT vapors, harboring a fusion of the yqjF gene promoter to a reporter element. However, the DNT metabolite which is the direct inducer of yqjF, has not yet been identified, nor has the regulatory mechanism of the induction been clarified. We demonstrate here that the YhaJ protein, a member of the LysR type family, acts as a transcriptional regulator of yqjF activation, as well as of a panel of additional E. coli genes. This group of genes share a common sequence motif in their promoters, which is suggested here as a putative YhaJ-box. In addition, we have linked YhaJ to the regulation of quinol-like compound degradation in the cell, and identified yhaK as playing a role in the degradation of DNT

Conserved Vibrational Coherence in the Ultrafast Rearrangement of 2-Nitrotoluene Radical Cation

2-Nitrotoluene (2-NT) is a good model for both photolabile protecting groups for organic synthesis and the military explosive 2,4,6-trinitrotoluene (TNT). In addition to the direct C−NO2 bond-cleavage reaction that initiates detonation in TNT, 2-NT undergoes an H atom attack reaction common to the photolabile 2-nitrobenzyl group, which forms the aci-nitro tautomer. In this work, femtosecond pump−probe measure- ments with mass spectrometric detection and density functional theory (DFT) calculations demonstrate that the initially prepared vibrational coherence in the 2-NT radical cation (2- NT+) is preserved following H atom attack. Strong-field adiabatic ionization is used to prepare 2-NT+, which can overcome a modest 0.76 eV energy barrier to H atom attack to form the aci-nitro tautomer as soon as ∼20−60 fs after ionization. Once formed, the aci-nitro tautomer spontaneously loses −OH to form C7H6NO+, which exhibits distinctly faster oscillations in its ion yield (290 fs period) as compared to the 2-NT+ ion (380 fs period). The fast oscillations are attributed to the coherent torsional motion of the aci-nitro tautomer, which has a significantly faster computed torsional frequency (86.9 cm−1) than the 2- NT+ ion (47.9 cm−1). Additional DFT calculations identify reaction pathways leading to the formation of the dissociation products C7H6NO+, C7H7+, and C6H6N+. Collectively, these results reveal a rich picture of coherently and incoherently driven dissociation pathways in 2-NT+

Microbial population changes during bioremediation of nitroaromatic - and nitramine-contaminated lagoon

Nitration reactions of aromatic compounds are commonly involved in military industrial processes. Military industries treated their process effluents using lagoon systems for many years. In this study, the sediment of a lagoon was investigated from a bioremediation objective. The physico-chemical characterization of the sediments showed the organic nature of the sediment (25.4% carbon with a C:N ¼ 3) highly concentrated in RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine), HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine) as well as two herbicides Dinoterb (2-tert-butyl-4,6-dinitrophenol) and Dinoseb (2-sec-butyl-4,6-dinitrophenol). Analysis of the 16S rRNA gene clone library revealed the presence of three dominant families, Geobacteriacea, Clostridiaceae and Pseudomonaceae. A bioremediation assay was carried out in anaerobic conditions in order to degrade organic compounds. In these conditions, 100% of Dinoterb and Dinoseb were degraded after 75 days of culture, while RDX and HMX were not consumed. The 16S rRNA gene clone library analysis of this incubation showed a drastic reduction of the final biodiversity composed by clones related to Enterobacteriaceae (especially Leclercia adecarboxylata) and Pseudomonaceae family. It was then suggested that Enterobacteriaceae and Pseudomonaceae were potentially involved in biodegradation of these two herbicides. To confirm this hypothesis, cultures were carried out with isolated species of Pseudomonas putida, Pseudomonas citronellolis and L. adecarboxylata in the presence of Dinoterb. The data confirmed that in the presence of glucose, these microorganisms are able to consume Dinoterb

Phenotypic evolution in microalgae: a dramatic morphological shift in Dictyosphaerium chlorelloides (Chlorophyta) after exposure to TNT

Phenotypic evolution in microalgae: a dramatic morphological shift in Dictyosphaerium chlorelloides (Chlorophyta) after exposure to TNT. The occurrence of rapid morphological evolution in the microalga Dictyosphaerium chlorelloides (Chlorophyta) was induced after exposure of the wild strains of the alga to the potent algal poison 2,4,6-trinitrotoluene (TNT). After exposing a wildtype population (consisted of representative spherical-ellipsoidal cells) to doses of TNT that were lethal for most of the cells, a TNT-resistant spindle-shaped mutant was able to proliferate. This spindleshaped mutant appeared spontaneously by rare mutations before the selective treatment: in deed, it was already present in the wild population. The frequency of the mutants within the ancestral population seemed to be determined by the balance between the rate of accumulation by recurrent mutation and the rate of elimination by selection (ranging 10-102 spindle-shaped mutants per 106 cells). We hypothesize that clone selection could take place in asexual populations of microalgae by selection of rare, pre-selective genotypes, driven by a drastic selective pressure subsequent to a catastrophic environmental changeEvolucion fenotípica en microalgas: un cambio morfológico espectacular en Dictyosphaerium chlorelloides (Chlorophyta) tras la exposición a TNT. Un cambio morfológico muy rápido tiene lugar en Dictyosphaerium chlorelloides (Chlorophyta) tras la exposición de cepas salvajes al potente alguicida 2,4,6 trinitrotolueno (TNT). Las cepas salvajes, sensibles al TNT, tienen una morfología típica esférico-elipsoidal. Tras exponer dichas cepas a dosis letales de TNT, solamente sobreviven células resistentes al tóxico cuya silueta es fusiforme. Estos resistentes fusiformes aparecen como consecuencia de mutaciones espontáneas que tienen lugar antes de exponer las cepas salvajes al agente selectivo (TNT): es decir, las células fusiformes estaban presentes en la población salvaje. La frecuencia de mutantes fusiformes en las poblaciones salvajes está definida por el equilibrio entre la tasa de acumulación de mutantes y la tasa en que son eliminados por tener una eficiencia biológica menor (10-102 mutantes fusiformes por 106 células salvajes). Se propone que la selección de clones podría ser un mecanismo de evolución adaptativa en poblaciones de microalgas asexuales. Este evento opera mediante la selección de genotipos pre-selectivos que aparecen como consecuencia del incremento de la presión de selección como fruto de eventos catastróficos en el medio ambient

Three-phase packed bed reactor with an evaporating solvent—I. Experimental: the hydrogenation of 2,4,6-trinitrotoluene in methanol

In this paper we present experimental data on the three-phase hydrogenation of 2,4,6-trinitrotoluene (TNT) to triaminotoluene. The experiments are performed in a cocurrent upflow packed bed reactor. Methanol is used as an evaporating solvent. The influence of the main operating parameters, the reactor pressure, the feed temperature and the molar ratio of hydrogen to TNT in the feed, are investigated experimentally. A rapid deactivation of the catalyst was observed. The rate of deactivation was investigated by performing experiments at standardized conditions at regular time intervals and by continuous operation of the reactor. Several experiments were done to find out if the catalyst could be regenerated in situ. This regeneration proved successful: the catalyst activity was practically equal to the initial one

A study of methods for the purification and the removal of color from trinitrotoluene wash waters

Symmetrical Trinitrotoluene is stable in the presence of moisture, but the nonsymmetrical trinitrotoluenes permit replacement of a nitro group with the formation of a nitrated cresol and nitrous acid. Nitrated cresols form salts similar to the picrates. To avoid these nonsymmetrical trinitrotoluenes the Ordinance Department, U. S. A., requires that Grade I trinitrotoluene have a solidification point of at least 80.2⁰C.². Numerous methods for purifying the crude trinitrotoluene and others for separating the nitrotoluenes have been suggested --Introduction, page 1

Nanoparticles in explosives detection – the state-of-the-art and future directions

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