Role of Nitrogen Limitation in Transformation of RDX (Hexahydro-1,3,5-Trinitro-1,3,5-Triazine) by Gordonia sp. Strain KTR9

Indest, Karl J.; Hancock, Dawn E.; Jung, Carina M.; Eberly, Jed O.; Mohn, William W.; Eltis, Lindsay D.; Crocker, Fiona H.

doi:10.1128/aem.03905-12

Cited by 27 publications

(14 citation statements)

References 31 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…KTR9. In agreement with our findings, studies of an xplR knockout demonstrated that XplR is not involved in RDX degradation (29). Studies of the xplAB-containing gene cluster in Gordonia sp.…”

Section: Discussionsupporting

confidence: 80%

“…In agreement with our findings, previous studies using Gordonia sp. KTR9 and a global nitrogen regulation (glnR) mutant of KTR9 indicated that nitrogen availability plays a role in the regulation of xplA (29). Beyond this conclusion, our studies also show that RDX removal was further increased in cells grown in RDX prior to resting-cell assays, and under these conditions, XplA protein and activity levels increased correspondingly.…”

Section: Discussionsupporting

confidence: 61%

See 1 more Smart Citation

Analysis of the xplAB -Containing Gene Cluster Involved in the Bacterial Degradation of the Explosive Hexahydro-1,3,5-Trinitro-1,3,5-Triazine

Chong

Sabir

Lorenz

et al. 2014

Appl Environ Microbiol

View full text Add to dashboard Cite

c Repeated use of the explosive compound hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) on military land has resulted in significant soil and groundwater pollution. Rates of degradation of RDX in the environment are low, and accumulated RDX, which the U.S. Environmental Protection Agency has determined is a possible human carcinogen, is now threatening drinking water supplies. RDX-degrading microorganisms have been isolated from RDX-contaminated land; however, despite the presence of these species in contaminated soils, RDX pollution persists. To further understand this problem, we studied RDX-degrading species belonging to four different genera (Rhodococcus, Microbacterium, Gordonia, and Williamsia) isolated from geographically distinct locations and established that the xplA and xplB (xplAB) genes, which encode a cytochrome P450 and a flavodoxin redox partner, respectively, are nearly identical in all these species. Together, the xplAB system catalyzes the reductive denitration of RDX and subsequent ring cleavage under aerobic and anaerobic conditions. In addition to xplAB, the Rhodococcus species studied here share a 14-kb region flanking xplAB; thus, it appears likely that the RDX-metabolizing ability was transferred as a genomic island within a transposable element. The conservation and transfer of xplAB-flanking genes suggest a role in RDX metabolism. We therefore independently knocked out genes within this cluster in the RDX-degrading species Rhodococcus rhodochrous 11Y. Analysis of the resulting mutants revealed that XplA is essential for RDX degradation and that XplB is not the sole contributor of reducing equivalents to XplA. While XplA expression is induced under nitrogen-limiting conditions and further enhanced by the presence of RDX, MarR is not regulated by RDX.

show abstract

Section: Discussionsupporting

confidence: 80%

Section: Discussionsupporting

confidence: 61%

Analysis of the xplAB -Containing Gene Cluster Involved in the Bacterial Degradation of the Explosive Hexahydro-1,3,5-Trinitro-1,3,5-Triazine

Chong

Sabir

Lorenz

et al. 2014

Appl Environ Microbiol

View full text Add to dashboard Cite

show abstract

“…4a). In all four cases, the ammonium concentration decreased to undetectable levels after 6 h. Previously, growing cultures of wild-type KTR9 and the glnR mutant with excess nitrogen exhibited a similar pattern of ammonium utilization (Indest et al 2013). Thus, RDX does not inhibit assimilation of ammonium by either strain.…”

Section: N Assimilation In Cell Suspensionsmentioning

confidence: 86%

“…A previous study (Indest et al 2013) concluded that the putative regulatory protein XplR, encoded by a gene located upstream of the xplAB gene cluster in KTR9, does not appear to regulate RDX degradation. The current study found that the global regulator of N assimilation, GlnR, is essential for KTR9 to degrade RDX and use it as an N source, but GlnR is not essential for xplA transcription.…”

Section: Discussionmentioning

confidence: 98%

“…In Mycobacterium tuberculosis, GlnR positively regulates the transcription of nirBD encoding nitrite reductase, and an M. tuberculosis glnR deletion mutant failed to grow on nitrate as the sole nitrogen source (Malm et al 2009). A recent transcriptomic analysis of KTR9 and its glnR mutant showed that nitrogen availability is an important determinant of RDX degradation and xplA gene expression (Indest et al 2013). Under Nlimiting conditions, a suite of genes, including xplA, was expressed at a lower level in the glnR mutant than in the wild type.…”

Section: Introductionmentioning

confidence: 97%

See 1 more Smart Citation

The essential role of nitrogen limitation in expression of xplA and degradation of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in Gordonia sp. strain KTR9

Zhu

Reuther

Liu

et al. 2014

Appl Microbiol Biotechnol

Self Cite

View full text Add to dashboard Cite

Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) is a widely used explosive and a major soil and groundwater contaminant. Organisms such as Gordonia sp. KTR9, capable of degrading RDX and using it as an N source, may prove useful for bioremediation of contaminated sites. XplA is a cytochrome P450 monooxygenase responsible for RDX degradation. Expression of xplA in KTR9 was not induced by RDX but was strongly induced (50-fold) during N-limited growth. When glnR, encoding a regulatory protein affecting N assimilation in diverse Actinobacteria, was deleted from KTR9, the bacterium lost the ability to use nitrate, nitrite, and RDX as N sources. Deletion of glnR also abolished the inhibition of xplA expression by nitrite. Our results confirm the essential role of GlnR in regulating assimilation of nitrite, but there was no evidence for a direct role of GlnR in regulating XplA expression. Rather, the general availability of nitrogen repressed XplA expression. We conclude that the inability of the glnR mutant to use RDX as an N source was due to its inability to assimilate nitrite, an intermediate in the assimilation of nitrogen from RDX. Regulation of XplA does not seem adaptive for KTR9, but it is important for RDX bioremediation with KTR9 or similar bacteria.

show abstract

Biostimulation and microbial community profiling reveal insights on RDX transformation in groundwater

et al. 2016

View full text Add to dashboard Cite

Hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine (RDX) is a high explosive released to the environment as a result of weapons manufacturing and testing worldwide. At Los Alamos National Laboratory, the Technical Area (TA) 16 260 Outfall discharged high‐explosives‐bearing water from a high‐explosives‐machining facility to Cañon de Valle during 1951 through 1996. These discharges served as a primary source of high‐explosives and inorganic‐element contamination in the area. Data indicate that springs, surface water, alluvial groundwater, and perched‐intermediate groundwater contain explosive compounds, including RDX (hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine); HMX (octahydro‐1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocine); and TNT (2,4,6‐trinitrotoluene). RDX has been detected in the regional aquifer in several wells, and a corrective measures evaluation is planned to identify remedial alternatives to protect the regional aquifer. Perched‐intermediate groundwater at Technical Area 16 is present at depths from 650 ft to 1200 ft bgs. In this study, we examined the microbial diversity in a monitoring well completed in perched‐intermediate groundwater contaminated by RDX, and examined the response of the microbial population to biostimulation under varying geochemical conditions. Results show that the groundwater microbiome was dominated by Actinobacteria and Proteobacteria. A total of 1,605 operational taxonomic units (OTUs) in 96 bacterial genera were identified. Rhodococcus was the most abundant genus (30.6%) and a total of 46 OTUs were annotated as Rhodococcus. One OTU comprising 25.2% of total sequences was closely related to a RDX ‐degrading strain R. erythropolis HS4. A less abundant OTU from the Pseudomonas family closely related to RDX‐degrading strain P. putida II‐B was also present. Biostimulation significantly enriched Proteobacteria but decreased/eliminated the population of Actinobacteria. Consistent with RDX degradation, the OTU closely related to the RDX‐degrading P. putida strain II‐B was specifically enriched in the RDX‐degrading samples. Analysis of the accumulation of RDX‐degradation products reveals that during active RDX degradation, there is a transient increase in the concentration of the degradation products MNX, DNX, TNX, and NDAB. The accumulation of these degradation products suggests that RDX is degraded via sequential reduction of the nitro functional groups followed by abiotic ring‐cleavage. The results suggest that strict anaerobic conditions are needed to stimulate RDX degradation under the TA‐16 site‐specific conditions.

show abstract

Role of Nitrogen Limitation in Transformation of RDX (Hexahydro-1,3,5-Trinitro-1,3,5-Triazine) by Gordonia sp. Strain KTR9

Cited by 27 publications

References 31 publications

Analysis of the xplAB -Containing Gene Cluster Involved in the Bacterial Degradation of the Explosive Hexahydro-1,3,5-Trinitro-1,3,5-Triazine

Analysis of the xplAB -Containing Gene Cluster Involved in the Bacterial Degradation of the Explosive Hexahydro-1,3,5-Trinitro-1,3,5-Triazine

The essential role of nitrogen limitation in expression of xplA and degradation of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in Gordonia sp. strain KTR9

Biostimulation and microbial community profiling reveal insights on RDX transformation in groundwater

Contact Info

Product

Resources

About