Werlen C, Nishino SF, Spain JC
Swiss Federal Institute for Environmental Science and Technology (EAWAG), CH 8600 Dubendorf, Switzerland.
Appl Environ Microbiol. 1998 Nov;64(11):4185-93. doi: 10.1128/AEM.64.11.4185-4193.1998.
Complete metabolism of chlorinated benzenes is not a feature that is generally found in aerobic bacteria but is thought to be due to a novel recombination of two separate gene clusters. Such a recombination could be responsible for adaptation of a natural microbial community in response to contamination with synthetic chemicals. This hypothesis was tested in a chlorobenzene (CB)-contaminated aquifer. CB-degrading bacteria from a contaminated site were characterized for a number of years by examining a combination of growth characteristics and DNA-DNA hybridization, PCR, and DNA sequence data. The genetic information obtained for the CB pathway of the predominant microorganism, Ralstonia sp. strain JS705, revealed a unique combination of (partially duplicated) genes for chlorocatechol degradation and genes for a benzene-toluene type of aromatic ring dioxygenase. The organism was detected in CB-polluted groundwater by hybridizing colonies cultivated on low-strength heterotrophic media with probes for the CB pathway. Southern hybridizations performed to determine the organization of the CB pathway genes and the 16S ribosomal DNA indicated that CB-degrading organisms isolated from different wells at the site were identical to JS705. Physiological characterization by the Biolog test system revealed some differences. The genes for the aromatic ring dioxygenase and dihydrodiol dehydrogenase of JS705 were detected in toluene and benzene degraders from the same site. Our results suggest that recent horizontal gene transfer and genetic recombination of existing genes between indigenous microorganisms were the mechanisms for evolution of the catabolic pathway. Evolution of the CB pathway seems to have created the capacity for natural attenuation of CB at the contaminated site.
氯苯的完全代谢并非需氧细菌普遍具有的特征，而是被认为源于两个独立基因簇的一种新型重组。这种重组可能是自然微生物群落适应合成化学物质污染的原因。该假设在一个受氯苯（CB）污染的含水层中得到了验证。多年来，通过综合考察生长特性以及DNA - DNA杂交、聚合酶链式反应（PCR）和DNA序列数据，对来自污染场地的CB降解细菌进行了表征。关于优势微生物——罗尔斯通氏菌属（Ralstonia sp.）菌株JS705的CB代谢途径所获得的遗传信息，揭示了氯儿茶酚降解基因（部分重复）与苯 - 甲苯型芳香环双加氧酶基因的独特组合。通过用CB代谢途径的探针与在低强度异养培养基上培养的菌落进行杂交，在受CB污染的地下水中检测到了该微生物。为确定CB代谢途径基因和16S核糖体DNA的组织方式而进行的Southern杂交表明，从该场地不同井中分离出的CB降解微生物与JS705相同。利用Biolog测试系统进行的生理表征显示出一些差异。在来自同一场地的甲苯和苯降解菌中检测到了JS705的芳香环双加氧酶和二氢二醇脱氢酶基因。我们的结果表明，近期本地微生物之间的水平基因转移和现有基因的遗传重组是分解代谢途径进化的机制。CB代谢途径的进化似乎在受污染场地产生了对CB进行自然衰减的能力。
