Biodegradation of cyclic nitramines by tropical marine sediment bacteria |
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Authors: | Manish Bhatt Jian-Shen Zhao Fanny Monteil-Rivera Jalal Hawari |
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Institution: | (1) Biotechnology Research Institute, National Research Council of Canada, 6100 Royalmount Avenue, Montreal, QC, H4P 2R2, Canada |
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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°C) anaerobically mineralized 69% or 57% (CO2, 25 days) of the total carbon of UL-14 C]-RDX (100 M) or UL-14 C]-HMX (10 M), respectively. As detected by PCR-DGGE, members of -proteobacteria (Halomonas), sulfate-reducing -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. |
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Keywords: | RDX HMX Unexploded ordnance Biodegradation Tropical marine sediment |
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