title: Cosubstrate independent mineralization of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) by a Desulfovibrio species under anaerobic conditions.
abstract: Past handling practices associated with the manufacturing and processing of the high explosive hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) has resulted in extensive environmental contamination. In-situ biodegradation is a promising technology for remediating RDX contaminated sites but often relies on the addition of a cosubstrate. A sulfate-reducing bacterium isolated from an RDX-degrading enrichment culture was studied for its ability to grow on RDX as a sole source of carbon and nitrogen and for its ability to mineralize RDX in the absence of a cosubstrate. The results showed the isolate degraded 140 muM RDX in 63 days when grown on RDX as a carbon source. Biomass within the carbon limited culture increased 9-fold compared to the RDX unamended controls. When the isolate was incubated with RDX as sole source of nitrogen it degraded 160 muM RDX in 41 days and exhibited a 4-fold increase in biomass compared to RDX unamended controls. Radiolabeled studies under carbon limiting conditions with (14)C-hexahydro-1,3,5-trinitro-1,3,5-triazine confirmed mineralization of the cyclic nitramine. After 60 days incubation 26% of the radiolabel was recovered as (14)CO(2), while in the control bottles less than 1% of the radiolabel was recovered as (14)CO(2). Additionally, approximately 2% of the radiolabeled carbon was found to be associated with the biomass. The 16S rDNA gene was sequenced and identified the isolate as a novel species of Desulfovibrio, having a 95.1% sequence similarity to Desulfovibrio desulfuricans. This is the first known anaerobic bacterium capable of mineralizing RDX when using it as a carbon and energy source for growth.
authors.affiliation: US Army Engineer Research & Development Center, Construction Engineering Research Laboratory, Champaign, IL 61822, USA. Clint.Arnett@usace.army.mil
authors.forename: Clint M
authors.initials: CM
authors.lastname: Arnett
authors.forename: Neal R
authors.initials: NR
authors.lastname: Adrian
mesh_terms: D000693:Anaerobiosis; D001673:Biodegradation, Environmental; D002244:Carbon / Q000378:metabolism; D004275:DNA, Ribosomal; D020564:Deltaproteobacteria / Q000378:metabolism*; D008855:Microscopy, Electron, Scanning; D008858:Microscopy, Phase-Contrast; D009584:Nitrogen / Q000378:metabolism; D010802:Phylogeny; D014227:Triazines / Q000737:chemistry / Q000378:metabolism*
chemical_list: D004275:DNA, Ribosomal; D014227:Triazines; D002244:Carbon; D009584:Nitrogen; C009160:cyclonite