Microaerophilic degradation of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) by three Rhodococcus strains

Fuller, Mark E.; Perreault, Nancy N.; Hawari, Jalal

doi:10.1111/j.1472-765x.2010.02897.x

Cited by 38 publications

(20 citation statements)

References 27 publications

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“…As suggested by Bernstein et al (2010), the groundwater flow directions in the aquifer change due to alterations in pumping, and this may be why RDX was not detected in borehole T4 in the past, but the potential for its degradation was detected in this study. The detection of aerobic degradation potential in microaerophilic sections of the aquifer (borehole T101) can be explained by the fact that under these conditions, degradation of RDX by microorganisms carrying the xplA gene can occur via the methylenedinitramine (MEDINA) pathway (Jackson et al 2007;Fuller et al 2010).…”

Section: Resultsmentioning

confidence: 99%

“…In vitro, this aerobic enzymatic activity with NADPH as an electron donor results in the formation of 4-nitro-2,4-diazabutanal (NDAB) (Jackson et al 2007). This activity has also been demonstrated in vivo for the Rhodococcus strains DN22 (Bhushan et al 2003;Coleman et al 2002;Fournier et al 2002), 11Y (Seth-Smith et al 2008) and YH1 (Nejidat et al 2008;Tekoah et al 1999) as well as under microaerophilic conditions by various other Rhodococcus strains (Fuller et al 2010).…”

Section: Introductionmentioning

confidence: 87%

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Isolation and characterization of RDX-degrading Rhodococcus species from a contaminated aquifer

et al. 2011

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Groundwater contamination by the explosive hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) is a global problem. Israel's coastal aquifer was contaminated with RDX. This aquifer is mostly aerobic and we therefore sought aerobic bacteria that might be involved in natural attenuation of the compound in the aquifer. RDX-degrading bacteria were captured by passively sampling the indigenous bacteria onto sterile sediments placed within sampling boreholes. Aerobic RDX biodegradation potential was detected in the sediments sampled from different locations along the plume. RDX degradation with the native sampled consortium was accompanied by 4-nitro-2,4-diazabutanal formation. Two bacterial strains of the genus Rhodococcus were isolated from the sediments and identified as aerobic RDX degraders. The xplA gene encoding the cytochrome P450 enzyme was partially (~500 bp) sequenced from both isolates. The obtained DNA sequences had 99% identity with corresponding gene fragments of previously isolated RDX-degrading Rhodococcus strains. RDX degradation by both strains was prevented by 200 μM of the cytochrome P450 inhibitor metyrapone, suggesting that cytochrome P450 indeed mediates the initial step in RDX degradation. RDX biodegradation activity by the T7 isolate was inhibited in the presence of nitrate or ammonium concentrations above 1.6 and 5.5 mM, respectively (100 mg l(-1)) while the T9N isolate's activity was retarded only by ammonium concentrations above 5.5 mM. This study shows that bacteria from the genus Rhodococcus, potentially degrade RDX in the saturated zone as well, following the same aerobic degradation pathway defined for other Rhodococcus species. RDX-degrading activity by the Rhodococcus species isolate T9N may have important implications for the bioremediation of nitrate-rich RDX-contaminated aquifers.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 87%

Isolation and characterization of RDX-degrading Rhodococcus species from a contaminated aquifer

et al. 2011

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“…RDX can be biodegraded by a range of both anaerobic (Adrian and Sutherland 1999;Arnett and Adrian 2009;Fuller et al 2009;Hawari et al 2001;Zhang and Hughes 2003;Zhao et al 2004) and aerobic bacteria (Bernstein et al 2011;Fournier et al 2002;Fuller et al 2010a;Seth-Smith et al 2002;Thompson et al 2005). In situ anaerobic bioremediation of RDX (and other explosives) has been demonstrated at several sites (Hatzinger and Lippincott 2012;Michalsen et al 2013;Newell 2008;Wade et al 2010).…”

Section: Introductionmentioning

confidence: 95%

Laboratory evaluation of bioaugmentation for aerobic treatment of RDX in groundwater

et al. 2014

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The potential for bioaugmentation with aerobic explosive degrading bacteria to remediate hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) contaminated aquifers was demonstrated. Repacked aquifer sediment columns were used to examine the transport and RDX degradation capacity of the known RDX degrading bacterial strains Gordonia sp. KTR9 (modified with a kanamycin resistance gene) Pseudomonas fluorescens I-C, and a kanamycin resistant transconjugate Rhodococcus jostii RHA1 pGKT2:Km+. All three strains were transported through the columns and eluted ahead of the conservative bromide tracer, although the total breakthrough varied by strain. The introduced cells responded to biostimulation with fructose (18 mg L(-1), 0.1 mM) by degrading dissolved RDX (0.5 mg L(-1), 2.3 µM). The strains retained RDX-degrading activity for at least 6 months following periods of starvation when no fructose was supplied to the column. Post-experiment analysis of the soil indicated that the residual cells were distributed along the length of the column. When the strains were grown to densities relevant for field-scale application, the cells remained viable and able to degrade RDX for at least 3 months when stored at 4 °C. These results indicate that bioaugmentation may be a viable option for treating RDX in large dilute aerobic plumes.

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“…14 Recently, aerobic RDX-degrading Rhodococcus have been isolated from the microaerophilic zone (0.9 mg l −1 dissolved oxygen) of a RDX-contaminated aquifer 15 and slow RDX degradation by Rhodococci has been reported under extreme microaerophilic conditions (<0.04 mg L −1 dissolved oxygen). 13 The corresponding genes, xplA and xplB, were first identified in Rhodococcus rhodochrous 11Y, 16 but have since been found in many genera of the Corynebacterineae that can use RDX as the sole N source. The xplA gene is highly conserved among RDX degrading bacteria from geographically distinct regions including North America, 17 Australia, 16 the United Kingdom, 16 and Israel, 15 suggesting XplA evolved following the introduction of RDX into the environment and rapidly spread across the world by horizontal gene transfer.…”

Section: ■ Introductionmentioning

confidence: 99%

“…Aerobic XplA-containing Rhodococcus have been isolated from RDX-contaminated soils 16 and from a microaerophilic aquifer. 15 Because RDX degradation by Rhodococcus strains was shown to be possible under extremely microaerophilic conditions, 13 it is reasonable to presume that Rhodococcus can degrade the anaerobically formed nitroso in micro-oxic environments. They would also degrade the nitroso compounds that may migrate to the oxic zone.…”

mentioning

confidence: 99%

Biodegradation of RDX Nitroso Products MNX and TNX by Cytochrome P450 XplA

Halasz

Manno

Perreault

et al. 2012

Environ. Sci. Technol.

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Anaerobic transformation of the explosive RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine) by microorganisms involves sequential reduction of N−NO 2 to the corresponding N−NO groups resulting in the initial formation of MNX (hexahydro-1-nitroso-3,5-dinitro-1,3,5-triazine). MNX is further reduced to the dinitroso (DNX) and trinitroso (TNX) derivatives. In this paper, we describe the degradation of MNX and TNX by the unusual cytochrome P450 XplA that mediates metabolism of RDX in Rhodococcus rhodochrous strain 11Y. XplA is known to degrade RDX under aerobic and anaerobic conditions, and, in the present study, was found able to degrade MNX to give similar products distribution including NO 2 − , NO 3 − , N 2 O, and HCHO but with varying stoichiometric ratio, that is, 2.06, 0.33, 0.33, 1.18, and 1.52, 0.15, 1.04, 2.06, respectively. In addition, the ring cleavage product 4-nitro-2,4,-diazabutanal (NDAB) and a trace amount of another intermediate with a [M-H] − at 102 Da, identified as ONNHCH 2 NHCHO (NO-NDAB), were detected mostly under aerobic conditions. Interestingly, degradation of TNX was observed only under anaerobic conditions in the presence of RDX and/or MNX. When we incubated RDX and its nitroso derivatives with XplA, we found that successive replacement of N−NO 2 by N− NO slowed the removal rate of the chemicals with degradation rates in the order RDX > MNX > DNX, suggesting that denitration was mainly responsible for initiating cyclic nitroamines degradation by XplA. This study revealed that XplA preferentially cleaved the N−NO 2 over the N−NO linkages, but could nevertheless degrade all three nitroso derivatives, demonstrating the potential for complete RDX removal in explosives-contaminated sites.

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Microaerophilic degradation of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) by three Rhodococcus strains

Cited by 38 publications

References 27 publications

Isolation and characterization of RDX-degrading Rhodococcus species from a contaminated aquifer

Isolation and characterization of RDX-degrading Rhodococcus species from a contaminated aquifer

Laboratory evaluation of bioaugmentation for aerobic treatment of RDX in groundwater

Biodegradation of RDX Nitroso Products MNX and TNX by Cytochrome P450 XplA

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