Biodegradation of nitro-substituted explosives 2,4,6-trinitrotoluene, hexahydro-1,3,5-trinitro-1,3,5-triazine, and octahydro-1,3,5,7-tetranitro-1,3,5-tetrazocine by a phytosymbiotic Methylobacterium sp. associated with poplar tissues (Populus deltoides x nigra DN34).
A pink-pigmented symbiotic bacterium was isolated from hybrid poplar tissues (Populus deltoides x nigra DN34). The bacterium was identified by 16S and 16S-23S intergenic spacer ribosomal DNA analysis as a Methylobacterium sp. (strain BJ001). The isolated bacterium was able to use methanol as the sole source of carbon and energy, which is a specific attribute of the genus Methylobacterium. The bacterium in pure culture was shown to degrade the toxic explosives 2,4,6-trinitrotoluene (TNT), hexahydro-1,3,5-trinitro-1,3,5-triazene (RDX), and octahydro-1,3,5,7-tetranitro-1,3,5-tetrazocine (HMX). [U-ring-(14)C]TNT (25 mg liter(-1)) was fully transformed in less than 10 days. Metabolites included the reduction derivatives amino-dinitrotoluenes and diamino-nitrotoluenes. No significant release of (14)CO(2) was recorded from [(14)C]TNT. In addition, the isolated methylotroph was shown to transform [U-(14)C]RDX (20 mg liter(-1)) and [U-(14)C]HMX (2.5 mg liter(-1)) in less than 40 days. After 55 days of incubation, 58.0% of initial [(14)C]RDX and 61.4% of initial [(14)C]HMX were mineralized into (14)CO(2). The radioactivity remaining in solution accounted for 12.8 and 12.7% of initial [(14)C]RDX and [(14)C]HMX, respectively. Metabolites detected from RDX transformation included a mononitroso RDX derivative and a polar compound tentatively identified as methylenedinitramine. Since members of the genus Methylobacterium are distributed in a wide diversity of natural environments and are very often associated with plants, Methylobacterium sp. strain BJ001 may be involved in natural attenuation or in situ biodegradation (including phytoremediation) of explosive-contaminated sites.
Van Aken
Benoit
B
Department of Civil and Environmental Engineering, The University of Iowa, Iowa City, Iowa 52242, USA. bvanaken@engineering.uiowa.edu
Yoon
Jong Moon
JM
Schnoor
Jerald L
JL
D001392:Azocines / Q000378:metabolism*; D001673:Biodegradation, Environmental; D003470:Culture Media; D021903:DNA, Ribosomal Spacer / Q000032:analysis; D006573:Heterocyclic Compounds, 1-Ring / Q000378:metabolism*; D020580:Methylobacterium / Q000145:classification / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D008969:Molecular Sequence Data; D010802:Phylogeny; D032107:Populus / Q000382:microbiology; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012338:RNA, Ribosomal, 23S / Q000235:genetics; D017422:Sequence Analysis, DNA; D013559:Symbiosis; D014227:Triazines / Q000378:metabolism*; D014303:Trinitrotoluene / Q000378:metabolism*
D001392:Azocines; D003470:Culture Media; D021903:DNA, Ribosomal Spacer; D006573:Heterocyclic Compounds, 1-Ring; D012336:RNA, Ribosomal, 16S; D012338:RNA, Ribosomal, 23S; D014227:Triazines; D014303:Trinitrotoluene; C007950:octogen; C009160:cyclonite