Genthner B R
University of West Florida Center for Environmental Diagnostics and Bioremediation, Pensacola 32514, USA.
Biodegradation. 1999 Feb;10(1):27-33. doi: 10.1023/a:1008348123672.
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.
脱氯是四个降解2-氯苯甲酸的产甲烷菌群中2,4-二氯苯氧乙酸生物降解的初始步骤。在由原始2,4-二氯苯氧乙酸菌群中脱氯活性最高的稀释液培养而成的菌群中，研究了邻位还原脱卤的特定特征，这些菌群分别命名为M34(-9)、P20(-9)、P21(-9)和M50(-7)。除2-氯苯甲酸外，这四个稀释菌群还对32种其他卤代芳香族底物中的4种进行了脱卤反应，包括2-溴苯甲酸、2,6-二氯苯甲酸、2,4-二氯苯甲酸和2-氯-5-羟基苯甲酸。脱卤反应仅发生在邻位。2,6-二氯苯甲酸的两个邻位氯都被去除。从2-溴苯甲酸和2,6-二氯苯甲酸中检测到了苯甲酸。2,4-二氯苯甲酸分别生成了4-氯苯甲酸，2-氯-5-羟基苯甲酸生成了3-羟基苯甲酸。只有苯甲酸进一步被降解。母体“苯甲酸分子”结构的轻微改变导致观察到除脱卤反应之外的还原生物转化。所有四个菌群都将2-氯苯甲醛还原为2-氯苄醇。四个菌群中的三个将2-氯苯甲醚进行了O-脱甲基反应，生成了2-氯苯酚。气相色谱-质谱分析表明，2-氯肉桂酸丙烯侧链中的双键被还原，生成了2-氯氢化肉桂酸。没有一种还原产物被脱氯。以下物质未发生脱卤反应：3-和4-溴苯甲酸、3-和4-氯苯甲酸、2-、3-和4-氟苯甲酸、2-、3-和4-碘苯甲酸、2-、3-和4-氯苯酚、2-氯苯胺、2-氯-5-甲基苯甲酸、2,3-二氯苯甲酸、2,5-二氯苯甲酸、2,4,5-三氯苯氧乙酸和2,4-二氯苯氧乙酸。M34(-9)、P20(-9)、P21(-9)和M50(-7)菌群在2-氯苯甲酸浓度≤4 mM时进行脱氯反应。P20(-9)菌群的脱氯速率最高，其次是M50(-7)菌群，在2 mM和3 mM 2,4-二氯苯氧乙酸以上时，脱氯速率分别下降。M34(-9)、P20(-9)、P21(-9)和M50(-7)菌群中主要的微生物生理类型是硫酸盐还原和利用氢气的厌氧菌。
