Abstract
Nitramines are key constituents of most of the explosives currently in use and consequently contaminate soil and groundwater at many military facilities around the world. Toxicity from nitramine contamination poses a health risk to plants and animals. Thus, understanding how nitramines are biodegraded is critical to environmental remediation. The biodegradation of synthetic nitramine compounds such as hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) has been studied for decades, but little is known about the catabolism of naturally produced nitramine compounds. In this study, we report the isolation of a soil bacterium, Variovorax sp. strain JS1663, that degrades N-nitroglycine (NNG), a naturally produced nitramine, and the key enzyme involved in its catabolism. Variovorax sp. JS1663 is a Gram-negative, non-sporeforming motile bacterium isolated from activated sludge based on its ability to use NNG as a sole growth substrate under aerobic conditions. A single gene (nnlA) encodes an iron-dependent enzyme that releases nitrite from NNG through a proposed β-elimination reaction. Bioinformatics analysis of the amino acid sequence of NNG lyase identified a PAS (Per-Arnt-Sim) domain. PAS domains can be associated with heme cofactors and function as signal sensors in signaling proteins. This is the first instance of a PAS domain present in a denitration enzyme. The NNG biodegradation pathway should provide the basis for the identification of other enzymes that cleave the NON bond and facilitate the development of enzymes to cleave similar bonds in RDX, nitroguanidine, and other nitramine explosives.
Original language | English |
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Article number | e00457-17 |
Journal | Applied and Environmental Microbiology |
Volume | 83 |
Issue number | 15 |
DOIs | |
State | Published - 2017 |
Funding
We thank Richard Giannone for assistance with high-resolution mass spectrometry analysis of NNG and glyoxylate and Jason T. Bouvier for reviewing the manuscript. This work was supported by the Strategic Environmental Research and Development Program (SERDP) under project WP-2332. Oak Ridge National Laboratory is managed by UT-Battelle, LLC, for the U. S. Department of Energy under contract no. DE-AC05-00OR22725.
Funders | Funder number |
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UT-Battelle | |
U.S. Department of Energy | DE-AC05-00OR22725 |
Oak Ridge National Laboratory | |
Strategic Environmental Research and Development Program | WP-2332 |
Keywords
- N-nitroglycine
- Naturally occurring nitro compound
- Nitramine degradation
- Streptomyces noursei
- Variovorax sp. strain JS1663