Bioelectromagnetics Genome-WideTranscription Analysis of Escherichia coli in Response to Extremely Low-Frequency Magnetic Fields Simona G. Huwiler, 1,2 * Christian Beyer, 3 Jˇrg Fro« hlich, 3 Hauke Hennecke, 1 Thomas Egli, 4,5 David Schˇrmann, 6 Hubert Rehrauer, 7 and Hans-Martin Fischer 1 1 Swiss Federal Institute of Technology (ETH Zurich), Institute of Microbiology, Zurich, Switzerland 2 University of Leipzig, Institute of Biochemistry, Leipzig, Germany 3 Swiss Federal Institute of Technology (ETH Zurich), Laboratory of Electromagnetic Fields and Microwave Electronics (IFH), Zurich, Switzerland 4 Eawag, Swiss Federal Institute forAquatic Science and Technology, Environmental Microbiology, Dˇbendorf, Switzerland 5 Swiss Federal Institute of Technology (ETH Zurich), Institute of Biogeochemistry and Pollutant Dynamics, Zurich, Switzerland 6 University of Basel, Institute of Biochemistry and Genetics, Department of Biomedicine, Basel, Switzerland 7 University of Zurich, Functional Genomics Center Zurich, Zurich, Switzerland The widespread use of electricity raises the question of whether or not 50 Hz (power line frequen- cy in Europe) magnetic fields (MFs) affect organisms. We investigated the transcription of Escherichia coli K-12 MG1655 in response to extremely low-frequency (ELF) MFs. Fields gener- ated by three signal types (sinusoidal continuous, sinusoidal intermittent, and power line intermit- tent; all at 50 Hz, 1 mT) were applied and gene expression was monitored at the transcript level using an Affymetrix whole-genome microarray. Bacterial cells were grown continuously in a chemostat (dilution rate D ¼ 0.4 h 1 ) fed with glucose-limited minimal medium and exposed to 50 Hz MFs with a homogenous flux density of 1 mT. For all three types of MFs investigated, neither bacterial growth (determined using optical density) nor culturable counts were affected. Likewise, no statistically significant change (fold-change > 2, P  0.01) in the expression of 4,358 genes and 714 intergenic regions represented on the gene chip was detected after MF expo- sure for 2.5 h (1.4 generations) or 15 h (8.7 generations). Moreover, short-term exposure (8 min) to the sinusoidal continuous and power line intermittent signal neither affected bacterial growth nor showed evidence for reliable changes in transcription. In conclusion, our experiments did not indicate that the different tested MFs (50 Hz, 1 mT) affected the transcription of E. coli. Bioelectromagnetics ß 2012 Wiley Periodicals, Inc. Key words: bacteria; chemostat; extremely low-frequency electromagnetic field (ELF-EMF); gene expression; microarray INTRODUCTION The use of electricity in everyday life has led to an increase in exposure to extremely low-frequency magnetic fields (ELF-MFs) at 50 Hz (power line fre- quency in Europe). This raises the question of wheth- er or not ELF-MFs may cause biological responses in living organisms. While this question has been addressed in numerous studies [Lacy-Hulbert et al., 1998; Volpe, 2003; WHO, 2007], it is extremely dif- ficult to extract common results and draw general conclusions. This is related to the facts that (i) differ- ent biological systems were investigated, including both prokaryotic organisms and eukaryotic cell Additional supporting information may be found in the online version of this article. Grant sponsor: OPO Foundation and Hamasil Foundation, Zurich, Switzerland. *Correspondence to: Simona G. Huwiler, University of Leipzig, Institute of Biochemistry, Bru ¨derstrasse 34, D-04103 Leipzig, Germany. E-mail: simona.huwiler@alumni.ethz.ch Received for review 11 April 2011; Accepted 11 January 2012 DOI 10.1002/bem.21709 Published online in Wiley Online Library (wileyonlinelibrary.com). ß 2012 Wiley Periodicals,Inc.