title: Preliminary characterization of four 2-chlorobenzoate-degrading anaerobic bacterial consortia.
abstract: Dechlorination was the initial step of 2CB biodegradation in four 2-chlorobenzoate-degrading methanogenic consortia. Selected characteristics of ortho reductive dehalogenation were examined in consortia developed from the highest actively dechlorinating dilutions of the original 2CB consortia, designated consortia M34(-9), P20(-9), P21(-9) and M50(-7). In addition to 2-chlorobenzoate, all four dilution consortia dehalogenated 4 of 32 additional halogenated aromatic substrates tested, including 2-bromobenzoate; 2,6-dichlorobenzoate; 2,4-dichlorobenzoate; and 2-chloro-5-hydroxybenzoate. Dehalogenation occurred exclusively at the ortho position. Both ortho chlorines were removed from 2,6-dichlorobenzoate. Benzoate was detected from 2-bromobenzoate and 2,6-dichlorobenzoate. 4-Chlorobenzoate and 3-hydroxybenzoate were formed from 2,4-dichlorobenzoate and 2-chloro-5-hydroxybenzoate, respectively. Only benzoate was further degraded. Slightly altering the structure of the parent "benzoate molecule" resulted in observing reductive biotransformations other than dehalogenation. 2-Chlorobenzaldehyde was reduced to 2-chlorobenzyl alcohol by all four consortia. 2-chloroanisole was O-demethoxylated by three of the four consortia forming 2-chlorophenol. GC-MS analysis indicated reduction of the double bond in the propenoic side chain of 2-chlorocinnamate forming 2-chlorohydrocinnamate. None of the reduction products was dechlorinated. The following were not dehalogenated: 3- and 4-bromobenzoate; 3- and 4-chlorobenzoate; 2-, 3-, and 4-fluorobenzoate; 2-, 3-, and 4-iodobenzoate; 2-, 3-, and 4-chlorophenol; 2-chloroaniline; 2-chloro-5-methylbenzoate; 2,3-dichlorobenzoate; 2,5-dichlorobenzoate; 2,4,5-trichlorophenoxyacetic acid; and 2,4-dichlorophenoxyacetic acid. Consortia M34(-9), P20(-9), P21(-9), and M50(-7) dechlorinated 2-chlorobenzoate at < or = 4 mm. Dechlorination rates were highest for consortia P20(-9) followed by those of M50(-7) with rates declining above 2 and 3 mm 2CB, respectively. The major physiological types of microorganisms in consortia M34(-9), P20(-9), P21(-9), and M50(-7) were sulfate-reducing and hydrogen-utilizing anaerobes.
authors.affiliation: University of West Florida Center for Environmental Diagnostics and Bioremediation, Pensacola 32514, USA. bgenthne@uwf.edu
authors.forename: B R
authors.initials: BR
authors.lastname: Genthner
mesh_terms: D001421:Bacteria, Anaerobic / Q000378:metabolism*; D001711:Biotransformation; D002713:Chlorine / Q000378:metabolism; D002723:Chlorobenzoates / Q000378:metabolism*; D008401:Gas Chromatography-Mass Spectrometry; D007700:Kinetics; D010084:Oxidation-Reduction; D011336:Probability
chemical_list: D002723:Chlorobenzoates; D002713:Chlorine; C060415:2-chlorobenzoic acid