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Applied and Environmental Microbiology, April 2006, p. 2775-2782, Vol. 72, No. 4
0099-2240/06/$08.00+0     doi:10.1128/AEM.72.4.2775-2782.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

Geobacter lovleyi sp. nov. Strain SZ, a Novel Metal-Reducing and Tetrachloroethene-Dechlorinating Bacterium{dagger}

Youlboong Sung,1,{ddagger} Kelly E. Fletcher,1 Kirsti M. Ritalahti,1 Robert P. Apkarian,6 Natalia Ramos-Hernández,3 Robert A. Sanford,4 Noha M. Mesbah,5 and Frank E. Löffler1,2*

School of Civil and Environmental Engineering,1 School of Biology, Georgia Institute of Technology, Atlanta, Georgia 30332-0512,2 Industrial Biotechnology Program, University of Puerto Rico, Mayagüez Campus, Mayagüez, Puerto Rico 00681-9012,3 Department of Geology, University of Illinois, Urbana, Illinois 61801-2352,4 Department of Microbiology, University of Georgia, Athens, Georgia 30602-2605,5 Integrated Microscopy and Microanalytical Facility, Department of Chemistry, Emory University, Atlanta, Georgia 303226

Received 8 December 2005/ Accepted 10 February 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, H2 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.

* Corresponding author. Mailing address: Georgia Institute of Technology, School of Civil and Environmental Engineering, 311 Ferst Drive, 3228 ES&T Building, Atlanta, GA 30332-0512. Phone: (404) 894-0279. Fax: (404) 894-8266. E-mail: frank.loeffler{at}ce.gatech.edu.

{dagger} In memory of Rob Apkarian. His microscopy skills and enthusiasm will truly be missed.

{ddagger} Present address: University of Oklahoma, Norman, OK 73019.

Applied and Environmental Microbiology, April 2006, p. 2775-2782, Vol. 72, No. 4
0099-2240/06/$08.00+0     doi:10.1128/AEM.72.4.2775-2782.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.



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