title: Sequential anaerobic degradation of 2,4-dichlorophenol in freshwater sediments.
abstract: 2,4-Dichlorophenol (2,4-DCP) was anaerobically degraded in freshwater lake sediments. From observed intermediates in incubated sediment samples and from enrichment cultures, the following sequence of transformations was postulated. 2,4-DCP is dechlorinated to 4-chlorophenol (4-CP), 4-CP is dechlorinated to phenol, phenol is carboxylated to benzoate, and benzoate is degraded via acetate to methane and CO2; at least five different organisms are involved sequentially. The rate-limiting step was the transformation of 4-CP to phenol. Sediment-free enrichment cultures were obtained which catalyzed only the dechlorination of 2,4-DCP, the carboxylation of phenol, and the degradation of benzoate, respectively. Whereas the dechlorination of 2,4-DCP was not inhibited by H2, the dechlorination of 4-CP, and the transformation of phenol and benzoate were. Low concentrations of 4-CP inhibited phenol and benzoate degradation. Transformation rates and maximum concentrations allowing degradation were determined in both freshly collected sediments and in adapted samples: at 31 degrees C, which was the optimal temperature for the dechlorination, the average adaptation time for 2,4-DCP, 4-CP, phenol, and benzoate transformations were 7, 37, 11 and 2 days, respectively. The maximal observed transformation rates for these compounds in acclimated sediments were 300, 78, 2, 130, and 2,080 micromol/liter(-1)/day(-1), respectively. The highest concentrations which still allowed the transformation of the compound in acclimated sediments were 3.1 m/M 2,4-DCP, 3.1 mM 4-CP, 13 mM phenol, and greater than 52 mM benzoate. The corresponding values were lower for sediments which had not been adapted for the transformation steps.
authors.affiliation: Department of Microbiology, University of Georgia, Athens 30602.
authors.forename: X
authors.initials: X
authors.lastname: Zhang
authors.forename: J
authors.initials: J
authors.lastname: Wiegel
mesh_terms: D000085:Acetates / Q000378:metabolism; D019342:Acetic Acid; D000693:Anaerobiosis; D001565:Benzoates / Q000378:metabolism; D019817:Benzoic Acid; D001673:Biodegradation, Environmental; D002245:Carbon Dioxide / Q000378:metabolism; D002733:Chlorophenols / Q000378:metabolism*; D005618:Fresh Water; D006859:Hydrogen / Q000378:metabolism; D007700:Kinetics; D008697:Methane / Q000378:metabolism; D019800:Phenol; D010636:Phenols / Q000378:metabolism; D014871:Water Microbiology; D014873:Water Pollutants; D014874:Water Pollutants, Chemical
chemical_list: D000085:Acetates; D001565:Benzoates; D002733:Chlorophenols; D010636:Phenols; D014873:Water Pollutants; D014874:Water Pollutants, Chemical; D002245:Carbon Dioxide; D019800:Phenol; C029107:4-chlorophenol; D006859:Hydrogen; D019817:Benzoic Acid; D008697:Methane; D019342:Acetic Acid; C004762:2,4-dichlorophenol