Microbial characterization of TNT-contaminated soils and anaerobic TNT degradation: high and unusual denitration activity

摘要

2,4,6-trinitrotoluene (TNT) is one of the most common explosives. In spite of its known toxic-ity and mutagenicity for many organisms, soils and groundwater are still frequently contaminated at manufacturing, disposal and TNT-destruction sites. Thirteen soil samples collected from a TNT-destruction field were investigated for their concentrations of TNT and its derivatives as well as for their microbial diversity. They contained TNT at various concentrations, ranging from 4 to 36 g TNT/kg soil. Various metabolites were also detected, including 2,4,6-trinitrobenzaldehyde, 4-amino-2,6-dinitrotoluene, 2-amino-4,6-dinitrotoluene and 2,4-dinitrotoluene. Microbial communities of these soil samples were characterized by 16S rRNA PCR-DGGE using bacterial universal primers. The DGGE patterns of these soil communities were compared with non-contaminated soils found at the same TNT-destruction site. Non-polluted soils revealed complex fingerprints of microorganisms while the contaminated samples showed the presence of dominant bands, indicating that a strong selection had occurred. The biodegradation capacities of a non-polluted and a TNT-contaminated soil were evaluated by enrichment cultures with TNT as sole N-source. High and unusual denitration activities were detected with the contaminated soil under defined anaerobic conditions.