Plasmids in the Degradation of Chlorinated Aromatic Compounds

Abstract

The soil-borne microbial community takes the “lion’s share” of the mineralization process of the ever-increasing input of man-made organic compounds in the biosphere, converting them to biomass or maintaining the balance of various elements in the soil (1). In the broad spectrum of stability of these compounds, halogen-substituted aromatic pollutants are of major concern because of their recalcitrance and magnitude of use (2). Haloaliphatic compounds possess shorter half-life in nature, most probably because of the presence of broad-specificity enzymes which can dehalogenate such compounds and are known to be active in Pseudomonas, Flavobacterium sp., and Moraxella sp. (3,4,5,6). In the past few years, isolation of pure cultures capable of degrading various compounds that are toxic and classified as recalcitrant, such as 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), 2,4-dichlorophenoxyacetic acid (2,4-D), pentachloro- phenol, etc., boosted up research in both the fields of basic understanding of the metabolic pathways of these compounds as well as in their potential use in decontamination technology (7,8,9,10,11).