Downloaded from www.microbiologyresearch.org by IP: 54.237.99.56 On: Wed, 31 Aug 2016 07:55:51 Geobacter anodireducens sp. nov., an exoelectrogenic microbe in bioelectrochemical systems Dan Sun, 1,2 Aijie Wang, 2,3 Shaoan Cheng, 1 Matthew Yates 4 and Bruce E. Logan 2,4 Correspondence Bruce E. Logan blogan@psu.edu Aijie Wang waj0578@hit.edu.cn 1 State Key Laboratory of Clean Energy Utilization, Department of Energy Engineering, Zhejiang University, Hangzhou 310027, PR China 2 State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology (SKLUWRE, HIT), Harbin 150090, PR China 3 Key Laboratory of Environmental Biotechnology, Research Center for Eco-Environmental Sciences, China Academy of Sciences, Beijing, PR China 4 Department of Civil and Environmental Engineering, The Pennsylvania State University, University Park, PA 16802, USA A previously isolated exoelectrogenic bacterium, strain SD-1 T , was further characterized and identified as a representative of a novel species of the genus Geobacter. Strain SD-1 T was Gram-negative, aerotolerant, anaerobic, non-spore-forming, non-fermentative and non-motile. Cells were short, curved rods (0.8–1.3 mm long and 0.3 mm in diameter). Growth of strain SD-1 T was observed at 15–42 6C and pH 6.0–8.5, with optimal growth at 30–35 6C and pH 7. Analysis of 16S rRNA gene sequences indicated that the isolate was a member of the genus Geobacter, with the closest known relative being Geobacter sulfurreducens PCA T (98 % similarity). Similar to other members of the genus Geobacter, strain SD-1 T used soluble or insoluble Fe(III) as the sole electron acceptor coupled with the oxidation of acetate. However, SD-1 T could not reduce fumarate as an electron acceptor with acetate oxidization, which is an important physiological trait for G. sulfurreducens. Moreover, SD-1 T could grow in media containing as much as 3 % NaCl, while G. sulfurreducens PCA T can tolerate just half this concentration, and this difference in salt tolerance was even more obvious when cultivated in bioelectrochemical systems. DNA–DNA hybridization analysis of strain SD-1 T and its closest relative, G. sulfurreducens ATCC 51573 T , showed a relatedness of 61.6 %. The DNA G+C content of strain SD-1 T was 58.9 mol%. Thus, on the basis of these characteristics, strain SD-1 T was not assigned to G. sulfurreducens, and was instead classified in the genus Geobacter as a representative of a novel species. The name Geobacter anodireducens sp. nov. is proposed, with the type strain SD-1 T (5CGMCC 1.12536 T 5KCTC 4672 T ). Direct extracellular electron transfer is a bioprocess that enables certain micro-organisms to transfer electrons to solid-state electron acceptors coupled with substrate oxid- ization. This process was initially discovered in the study of dissimilatory metal-reducing bacteria in order to under- stand global biogeochemical cycles (Lovley et al., 2004; Lovley & Phillips, 1986). Recently, it has been discovered that some of these microbes could produce electrical current using an electrode instead of minerals as an electron acceptor in bioelectrochemical systems (BESs) (Logan, 2008). These microbes, collectively called exoelectrogens, can be used for different purposes in BESs, such as electricity generation in microbial fuel cells (MFCs), hydrogen pro- duction in microbial electrolysis cells (MECs), metal reduc- tion and recovery, desalination, organic product synthesis and treatment of wastewaters (Logan & Rabaey, 2012). Exoelectrogenic micro-organisms, and the mechanisms used by these microbes to transfer electrons to the electrode, have been studied intensely in the past decade, resulting in a novel subdiscipline of microbiology called electromicro- biology (Lovley, 2012). However, our understanding of how Abbreviations: BES, bioelectrochemical system; MEC, microbial elec- trolysis cell; MFC, microbial fuel cell. The GenBank/EMBL/DDBJ accession number for the 16S rRNA gene sequence of strain SD-1 T is KF006333. Three supplementary figures and a supplementary table are available with the online Supplementary Material. International Journal of Systematic and Evolutionary Microbiology (2014), 64, 3485–3491 DOI 10.1099/ijs.0.061598-0 061598 G 2014 IUMS Printed in Great Britain 3485