Sung Youlboong, Fletcher Kelly E, Ritalahti Kirsti M, Apkarian Robert P, Ramos-Hernández Natalia, Sanford Robert A, Mesbah Noha M, Löffler Frank E
Georgia Institute of Technology, School of Civil and Environmental Engineering, 311 Ferst Drive, 3228 ES&T Building, Atlanta, GA 30332-0512, USA.
Appl Environ Microbiol. 2006 Apr;72(4):2775-82. doi: 10.1128/AEM.72.4.2775-2782.2006.
A bacterial isolate, designated strain SZ, was obtained from noncontaminated creek sediment microcosms based on its ability to derive energy from acetate oxidation coupled to tetrachloroethene (PCE)-to-cis-1,2-dichloroethene (cis-DCE) dechlorination (i.e., chlororespiration). Hydrogen and pyruvate served as alternate electron donors for strain SZ, and the range of electron acceptors included (reduced products are given in brackets) PCE and trichloroethene [cis-DCE], nitrate [ammonium], fumarate [succinate], Fe(III) [Fe(II)], malate [succinate], Mn(IV) [Mn(II)], U(VI) [U(IV)], and elemental sulfur [sulfide]. PCE and soluble Fe(III) (as ferric citrate) were reduced at rates of 56.5 and 164 nmol min(-1) mg of protein(-1), respectively, with acetate as the electron donor. Alternate electron acceptors, such as U(VI) and nitrate, did not inhibit PCE dechlorination and were consumed concomitantly. With PCE, Fe(III) (as ferric citrate), and nitrate as electron acceptors, H(2) was consumed to threshold concentrations of 0.08 +/- 0.03 nM, 0.16 +/- 0.07 nM, and 0.5 +/- 0.06 nM, respectively, and acetate was consumed to 3.0 +/- 2.1 nM, 1.2 +/- 0.5 nM, and 3.6 +/- 0.25 nM, respectively. Apparently, electron acceptor-specific acetate consumption threshold concentrations exist, suggesting that similar to the hydrogen threshold model, the measurement of acetate threshold concentrations offers an additional diagnostic tool to delineate terminal electron-accepting processes in anaerobic subsurface environments. Genetic and phenotypic analyses classify strain SZ as the type strain of the new species, Geobacter lovleyi sp. nov., with Geobacter (formerly Trichlorobacter) thiogenes as the closest relative. Furthermore, the analysis of 16S rRNA gene sequences recovered from PCE-dechlorinating consortia and chloroethene-contaminated subsurface environments suggests that Geobacter lovleyi belongs to a distinct, dechlorinating clade within the metal-reducing Geobacter group. Substrate versatility, consumption of electron donors to low threshold concentrations, and simultaneous reduction of electron acceptors suggest that strain SZ-type organisms have desirable characteristics for bioremediation applications.
从未受污染的小溪沉积物微观世界中分离出一株细菌，命名为SZ菌株。该菌株能够通过将乙酸氧化与四氯乙烯（PCE）还原为顺式-1,2-二氯乙烯（cis-DCE）（即氯呼吸作用）偶联来获取能量。氢气和丙酮酸可作为SZ菌株的替代电子供体，其电子受体范围包括（括号内为还原产物）PCE和三氯乙烯[cis-DCE]、硝酸盐[铵]、富马酸盐[琥珀酸盐]、Fe(III)[Fe(II)]、苹果酸盐[琥珀酸盐]、Mn(IV)[Mn(II)]、U(VI)[U(IV)]以及元素硫[硫化物]。以乙酸作为电子供体时，PCE和可溶性Fe(III)（以柠檬酸铁形式存在）的还原速率分别为56.5和164 nmol min⁻¹ mg蛋白质⁻¹。诸如U(VI)和硝酸盐等替代电子受体不会抑制PCE的脱氯作用，且会同时被消耗。以PCE、Fe(III)（以柠檬酸铁形式存在）和硝酸盐作为电子受体时，氢气分别被消耗至阈值浓度0.08±0.03 nM、0.16±0.07 nM和0.5±0.06 nM，乙酸分别被消耗至3.0±2.1 nM、1.2±0.5 nM和3.6±0.25 nM。显然，存在电子受体特异性的乙酸消耗阈值浓度，这表明与氢气阈值模型类似，乙酸阈值浓度的测定为描绘厌氧地下环境中的末端电子接受过程提供了一种额外的诊断工具。遗传和表型分析将SZ菌株归类为新物种Geobacter lovleyi sp. nov.的模式菌株，Geobacter（原Trichlorobacter）thiogenes为其最亲近的亲缘种。此外，从PCE脱氯菌群和氯乙烯污染的地下环境中回收的16S rRNA基因序列分析表明，Geobacter lovleyi属于金属还原Geobacter菌群内一个独特的脱氯分支。底物通用性、将电子供体消耗至低阈值浓度以及同时还原电子受体表明，SZ菌株型生物体具有生物修复应用所需的特性。
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