Diversity of reductive dechlorinating bacteria and archaea in herbicide/dioxin-contaminated soils from Bien Hoa airbase using metagenomic approach

Heavy herbicide/dioxin contamination of soil was derived a negative effect on the microbial biodiversity, soil quality, animal and human health in Central and South of Vietnam. This is the first time, the application metagenomic tools investigated soil microbial structural community of undetoxified (C - 21,605 ng TEQ/kg dry soil) and bioremediated (BHR - 13.2 ng TEQ/kg dry soil) which could not only help us to explore the potential risks associated with contaminated soils but also provide insights into possible soil bioremediation technology by stimulating indigenous microbes. Four methanogen genera, Methanosarcina (24 - 322 OTUs respectively C – BHR samples), Methanocella (13 - 63 OTUs), Methanosaeta (7 - 42 OTUs) and Methanococcus (6 - 69 OTUs) have been dominantly detected in both two metagenomes. Twenty genera of archaea belonging to the phylum Euryarchaeota were found. They could be clustered within 14 different families and nine archaeal genera including unclassified archaea (17 OTUs – C; 145 OTUs - BHR). In metagenome C and BHR, 12 genera of sulfate reducing bacteria (SRB) with different number (2 - 77; 61 - 904 OTUs) respectively were presented. Four SRB genera are dominated in C metagenome, it is linear also in BHR. The highest number is genus Desulfovibrio detected in both examined metagenomes. However, the relationship features of these bacterial groups need deeply investigation for understanding their role of reductive dechlorination, anaerobic degradation in herbicide/dioxin contaminated heavy soil and sediment. These results provide additional evidence to explain why heavy herbicide/dioxin contaminated soil was detoxified successfully at Bien Hoa airbase, Vietnam.

Biological effects of tourmaline treatment on Dehalococcoides spp. during the reductive dechlorination of trichloroethylene

To explore the application of mineral in bioremediation of contaminated aquifers, this study investigated tourmaline-induced changes in TCE degradation, community structure, cell proliferation and gene expression of dechlorinating bacteria.

Spatial Distribution of PCB Dechlorinating Bacteria and Activities in Contaminated Soil

Soil samples contaminated with Aroclor 1260 were analyzed for microbial PCB dechlorination potential, which is the rate-limiting step for complete PCB degradation. The average chlorines per biphenyl varied throughout the site suggesting that different rates ofin situdechlorination had occurred over time. Analysis of PCB transforming (aerobic and anaerobic) microbial communities and dechlorinating potential revealed spatial heterogeneity of both putative PCB transforming phylotypes and dechlorination activity. Some soil samples inhibited PCB dechlorination in active sediment from Baltimore Harbor indicating that metal or organic cocontaminants might cause the observed heterogeneity ofin situdechlorination. Bioaugmentation of soil samples contaminated with PCBs ranging from 4.6 to 265 ppm with a pure culture of the PCB dechlorinating bacteriumDehalobium chlorocoerciaDF-1 also yielded heterologous results with significant dechlorination of weathered PCBs observed in one location. The detection of indigenous PCB dehalorespiring activity combined with the detection of putative dechlorinating bacteria and biphenyl dioxygenase genes in the soil aggregates suggests that the potential exists for complete mineralization of PCBs in soils. However, in contrast to sediments, the heterologous distribution of microorganisms, PCBs, and inhibitory cocontaminants is a significant challenge for the development ofin situmicrobial treatment of PCB impacted soils.