Quinone Moieties Link the Microbial Respiration of Natural Organic Matter to the Chemical Reduction of Diverse Nitroaromatic Compounds

Abstract

Insensitive munitions compounds (IMCs) are emerging nitroaromatic contaminants developed by the military as safer-to-handle alternatives to conventional explosives. Biotransformation of nitroaromatics via microbial respiration has only been reported for a limited number of substrates. Important soil microorganisms can respire natural organic matter (NOM) by reducing its quinone moieties to hydroquinones. Thus, we investigated the NOM respiration combined with the abiotic reduction of nitroaromatics by the hydroquinones formed. First, we established nitroaromatic concentration ranges that were nontoxic to the quinone respiration. Then, an enrichment culture dominated by Geobacter anodireducens could indirectly reduce a broad array of nitroaromatics by first respiring NOM components or the NOM surrogate anthraquinone-2,6-disulfonate (AQDS). Without quinones, no nitroaromatic tested was reduced except for the IMC 3-nitro-1,2,4-triazol-5-one (NTO). Thus, the quinone respiration expanded the spectrum of nitroaromatics susceptible to transformation. The system functioned with very low quinone concentrations because NOM was recycled by the nitroaromatic reduction. A metatranscriptomic analysis demonstrated that the microorganisms obtained energy from quinone or NTO reduction since respiratory genes were upregulated when AQDS or NTO was the electron acceptor. The results indicated microbial NOM respiration sustained by the nitroaromatic-dependent cycling of quinones. This process can be applied as a nitroaromatic remediation strategy, provided that a quinone pool is available for microorganisms.

Metal-Free Activation of Sulfite by Benzoquinone-Derived Carbon for Efficient Organic Contaminant Degradation: Identification and Regulation of Active Sites

“…The quinone and hydroquinone groups on carbon catalysts have been previously identified as the most common couple for redox activities . Theoretically, electrophilic quinone/ketonic CO species preferentially reacts with nucleophilic S­(IV). ,, As an electron acceptor, quinones can accept electrons to produce semiquinone radical intermediates and hydroquinones. ,, Thus, if quinone groups were the main active sites for oxidative activation of Na 2 SO 3 , electron transfer from Na 2 SO 3 to quinone groups would be expected to lead to an increase in the content of semiquinone species. In this case, the EPR spectra were used to investigate the surface semiquinone species of the BQC-10 before and after the reaction (denoted as “used BQC-10”).…”

“…47,62,63 As an electron acceptor, quinones can accept electrons to produce semiquinone radical intermediates and hydroquinones. 18,64,65 Thus, if quinone groups were the main active sites for oxidative activation of Na 2 SO 3 , electron transfer from Na 2 SO 3 to quinone groups would be expected to lead to an increase in the content of semiquinone species. In this case, the EPR spectra were used to investigate the surface semiquinone species of the BQC-10 before and after the reaction (denoted as "used BQC-10").…”

Genome-Centric Metatranscriptomic Characterization of a Humin-Facilitated Anaerobic Tetrabromobisphenol A-Dehalogenating Consortium

“…48 Humic substances including humin, humic acid, and fulvic acid generally act as electron shuttles in the extracellular electron transport owing to their multiple redoxactive moieties such as quinones, thiols, disulfides, and nitrogen functional groups. 57,58 Soluble humic acid is well studied for shuttling electrons, for example, between Geobacter metallireducens and Fe(III) oxide. 57 Humin, an insoluble component of humic substances, might play a similar role in mediating electrons.…”

Unveiling the corrosion mechanism of 3-nitro-1,2,4-triazol-5-one (NTO) toward mild steel from ab initio molecular dynamics: how the “nitro-to-amino” reaction matters

“…[23][24][25] NTO can be easily released into the environment during production, transportation and use; therefore, it has the potential to cause an acidication of the soil solution, which will negatively impact the aquatic biota and mobilizing metals. 23 Recently, in light of the increasing use of NTO and the inevitable requirement for environmental protection, various methods for treating NTO wastewater have been developed, including chemical degradation, [26][27][28] biodegradation, [29][30][31] abiotic transformation 24,[32][33][34][35] and adsorption. 36,37 Experimentally, NTO has been observed to transform into 3-amino-1,2,4-triazol-5-one (ATO) during these treatments (details of the physico-chemical properties of NTO and ATO can be seen in Table S2 †) abiotically or biologically, through the reduction of nitro to amino.…”

“…36,37 Experimentally, NTO has been observed to transform into 3-amino-1,2,4-triazol-5-one (ATO) during these treatments (details of the physico-chemical properties of NTO and ATO can be seen in Table S2 †) abiotically or biologically, through the reduction of nitro to amino. 32 This reduction step is also considered a prerequisite for the transformation of NTO into innocuous products such as N 2 , CO 2 , NH 3 and urea. 30,33,38 While the NTO-to-ATO reaction has been experimentally conrmed, the atomic-level understanding of the reaction process remains ambiguous.…”