Sediments reductive metabolism

The refractory nature of some pollutants, notably, persistent polyhalogenated compounds, has raised problems of bioremediation of contaminated sites (e.g., sediments and dumping sites). There has been interest in the identification, or the production by genetic manipulation, of strains of microorganisms that can metabolically degrade recalcitrant molecules. For example, there are bacterial strains that can reductively dechlorinate PCBs under anaerobic conditions. 

Certain anaerobic bacteria can reductively dechlorinate PCBs in sediments (EHC 140). Higher chlorinated PCBs are degraded more rapidly than lower chlorinated ones, which is in contrast to the trend for oxidative metabolism described earlier. Genetically engineered strains of bacteria have been developed to degrade PCBs in bioremediation programs. 

Reductive dechlorination at positions with geminal chloro substituents is assumed to be the major way of degradation [83, 122,215]. The fact that Cl, C4, and C7 on bornane are never chlorinated leaves seven positions available. Therefore, dead-end metabohtes in an anaerobic miheu should be chlorobor-nanes with a maximum of seven chlorine atoms [216]. Chlorobornanes which have two hydrogens at one carbon such as B7-515 (P-32) and B8-806/B8-809 (P-42) should be degraded to hexachlorobornanes. Consequently, pentachlorobor-nanes were predicted as the final anaerobic metabolic products of B8-2229 (P-44) and B9-1025 (P-62) [216], and their presence could be recently confirmed in sediment samples [217],... 

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