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MICROBIAL DEGRADATION OF SYNTHETIC CHLORINATED COMPOUNDS: EVOLUTIONARY IMPLICATIONS
Citation:
Rothmel, R., R. Haughland, U. Sanodkar, W. Coco, AND A. Chakrabarty. MICROBIAL DEGRADATION OF SYNTHETIC CHLORINATED COMPOUNDS: EVOLUTIONARY IMPLICATIONS. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/A-93/132 (NTIS PB93204139), 1990.
Description:
Environmental release of synthetic chlorinated compounds in the form of herbicides/pesticides, solvents, refrigerants, etc., has created major concerns with regard to their effects on human health because of the persistence of many such compounds. he persistence of these compounds is a result of the inability of natural microorganisms to utilize them as a sole source of carbon and energy. any microorganisms can utilize simple chlorinated compounds such as 3-chlorobenzoate (3Cba) or 2,4-dichlorophenoxyacetate (2,4-D) as their sole carbon source but cannot utilize higher chlorinated forms such as 2,4,5-trichlorophenoxy acetic acid (2,4,5-T) and others. nder strong selection in a chemostat with 2,4,5-T as the only major source of carbon (directed evolution), it has been possible to isolate a strain of Pseudomonas cepacia AC1100 that can utilize 2,4,5-T as its sole source of carbon and energy. olecular cloning of the genes both for 3Cba/ 2,4-D as well as 2,4,5-T degradation has shown that while the chlorocatechol (clc) genes for 3Cba and 2,4-D dissimilation are highly homologous with one another and with the cat genes of catechol degradation, the 2,4,5-T degradative (tft) genes show no homology with any of the genomic DNA of a large number of pseudomonads and other bacteria. hus, while natural evolution encompasses recruitment of analogous genes and their subsequent divergence to provide new substrate specificity (for chlorinated compounds) to their-gene products, directed evolution such as that which occurred in the evolution of tft genes in P. cepacia AC1100 in the chmostat may involve recruitment of totally nonhomologous genes from ifferent species or genera in response to short-term, strong selection.
