| Abstract: | Chlorinated hydrocarbons are widely used because of their chemical and thermal stability as well as their fungicidal, herbicidal, and insecticidal properties. Unfortunately, it is just this stability that makes the compounds persistent in nature; half-lives of more than 15 years are not uncommon. In many countries the use of some chlorinated compounds has been prohibited, even though many such compounds (e.g., DDT) exhibit exactly the desired spectrum of effects. Surprisingly, microbiol systems that can degrade most chlorinated hydrocarbons have been found in nature. Indeed, it is possible, in many cases, to isolate pure cultures of bacteria that can utilize these compounds as the sole source of carbon and energy. Even polychlorinated compounds, such as the wood preservative and herbicide pentachlorophenol, can be utilized as a source of carbon by some bacteria. The study of the biodegradation of halogenated hydrocarbons has led to the discovery of novel catabolic pathways in which unusual and previously undescribed enzymatic activities have been detected. Bacterial enzymes have even been isolated that can replace halogen substituents in aliphatic and aromatic compounds with hydroxyl groups or hydrogen atoms. Improved understanding of the biodegradation of halogenated hydrocarbons, as described in this article, will almost certainly result in new biotechnological applications, especially in the area of waste-water treatment. |
