title: Biodegradation of cyclic nitramines by tropical marine sediment bacteria.
abstract: Undersea deposition of unexploded ordnance (UXO) constitutes a potential source of contamination of marine environments by hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX). The goal of the present study was to determine microbial degradation of RDX and HMX in a tropical marine sediment sampled from a coastal UXO field in the region of Oahu Island in Hawaii. Sediment mixed cultures growing in marine broth 2216 (21 degrees C) anaerobically mineralized 69% or 57% (CO2, 25 days) of the total carbon of [UL-14 C]-RDX (100 microM) or [UL-14 C]-HMX (10 microM), respectively. As detected by PCR-DGGE, members of gamma-proteobacteria (Halomonas), sulfate-reducing delta-proteobacteria (Desulfovibrio), firmicutes (Clostridium), and fusobacterium appeared to be dominant in RDX-enrichment and/or HMX-enrichment cultures. Among 22 sediment bacterial isolates screened for RDX and HMX biodegradation activity under anaerobic conditions, 5 were positive for RDX and identified as Halomonas (HAW-OC4), Marinobacter (HAW-OC1), Pseudoalteromonas (HAW-OC2 and OC5) and Bacillus (HAW-OC6) by their 16S rRNA genes. Sediment bacteria degraded RDX to N2O and HCHO via the intermediary formation of hexahydro-1-nitroso-3,5-dinitro-1,3,5-triazine (MNX) and methylenedinitramine. The present findings demonstrate that cyclic nitramine contaminants are likely to be degraded upon release from UXO into tropical marine sediment.
authors.affiliation: Biotechnology Research Institute, National Research Council of Canada, 6100 Royalmount Avenue, Montreal, QC H4P 2R2, Canada.
authors.forename: Manish
authors.initials: M
authors.lastname: Bhatt
authors.forename: Jian-Shen
authors.initials: JS
authors.lastname: Zhao
authors.forename: Fanny
authors.initials: F
authors.lastname: Monteil-Rivera
authors.forename: Jalal
authors.initials: J
authors.lastname: Hawari
mesh_terms: D001392:Azocines / Q000737:chemistry / Q000378:metabolism; D001419:Bacteria / Q000378:metabolism*; D001673:Biodegradation, Environmental; D001709:Biotechnology; D006254:Hawaii; D006573:Heterocyclic Compounds, 1-Ring / Q000737:chemistry / Q000378:metabolism; D008386:Marine Biology; D008903:Minerals / Q000378:metabolism; D012623:Seawater / Q000382:microbiology; D014227:Triazines / Q000737:chemistry / Q000378:metabolism*; D014303:Trinitrotoluene / Q000737:chemistry / Q000378:metabolism*; D014874:Water Pollutants, Chemical / Q000378:metabolism*
chemical_list: D001392:Azocines; D006573:Heterocyclic Compounds, 1-Ring; D008903:Minerals; D014227:Triazines; D014874:Water Pollutants, Chemical; D014303:Trinitrotoluene; C007950:octogen; C009160:cyclonite